Some of this may be obvious to you folks, but I just wanted to give a thorough overview of common equipment choices in PvP, IE what to bring for your build, and why it makes sense so you can make your own informed judgements. For now I am going to focus on 8v8 especially GvG, and ignore splits as we are trying to minimize them in our build, but splits can benefit from slightly different setups.
Martial Weapons
Inscriptions:
+15% damage > 50 HP is near always the preferred choice, because the condition is fairly easy to meet. If you fall below half for any decent length of time, you're probably dead anyway.
A few builds need +5 energy, most notably energy-intensive utility ranger like crippling shot, or some assassin combos. Both of those characters don't lose a whole lot from the extra damage, since Cripshots are all about conditions, and most assassin damage comes from skills. (the 15>50 only affects base weapon damage.)
Suffix: just about always Fortitude. Extra health provides the best protection against spikes and is especially beneficial when you are under DP.
Prefix: this is where things get interesting.
Vampiric is the primary weapon of most melee characters, because the life stealing has the best Damage per Second, and any health loss is usually mopped up by party heals. (often you gain health under vampiric anyway)
An elemental weapon is useful for attacking warriors, who have +20 armor against physical damage. You want to swap into this whenever attacking or spiking a warrior.
Zealous is useful on faster-attacking weapons for some builds, IE generally not hammers/scythes. Warriors can push frenzy more often if they pick up extra energy from zealous. You need to be vigilant about swapping out of it when you aren't attacking to avoid the energy degeneration.
Sundering, everyone's favorite, is only viable for the highest damage of weapons- scythes especially, and borderline for hammers. They have slightly less DPS, but they can randomly make larger spike damage if your critical and sundering chance trigger together. Some prefer that extra random damage for pushing a lucky kill through against strong defenses.
Characters with spammable, short-duration conditions often bring a condition-lengthing mod. A ranger with apply poision typically uses a poison bow, while a cripshot ranger will bring crippling. Warriors with a deep wound on the other hand don't bother, because deep wound is not applied often, and is so dangerous that the opponent should die if it isn't cleaned quickly anyway.
Shields for warriors/paragons always have fortitude mods. The default inscription is usually 20% blind reduction, but you may find switching to weakness or cripple reduction shields useful depending on what the opposing team is using to shut you down. Getting around blind is still the most beneficial if the enemy team has any at all, because blinds are for short durations and may be weathered out instead of being removed.
In addition to the above, rangers need to keep in mind their bow types. For condition-based rangers using apply poison or barbed arrows, recurve bows are favored for their superior flight speed, which makes interrupting much easier. Interrupting in a longbow can be a nightmare if you've tried it. For read-the-wind type rangers, flatbows are common.
While the flatbow normally has terrible flight time and an enormous arc, the extra speed from read the wind negates this, and these prep rangers want both the superior attack speed and distance a flatbow has to offer. Likewise this bow is vampiric so they can do additional direct damage. A short bow should be kept on swap in case Read the Wind is interrupted and disabled for a time, so you can keep up the fast attacks.
Finally, don't forget to customize your pvp weapons on pve characters: the +20% damage bonus is significant.
Caster Weapons:
A 40/40 set or two are the caster's mainstay. (20% faster cast and 20% recharge on (attribute) wand and focus.) You will want this for your one or two main spell attributes on your skillbar. Half recharge gives you much more flexibility on when you can use your skills, and makes your build more efficient if you have the energy. Half cast time is both for efficiency, but it also makes your skills harder to interrupt. Rangers and mesmers can interrupt even 3/4th-second cast skills on reflex, so hitting your half cast time affords some protection against that. It can also help you making a critical save like a heal or blind.
40/enchanting staves benefit a few builds. (20% + 20% faster cast on <attribute>, 20% enchanting, 20% built-in half spell recharge). Such a prot staff is a requirement for using Aegis, lengthing both the critical duration and making the long 2s cast less vulnerable to interrupts. Prot monks spend most of their time in this set, opting for extra enchantment duration over the faster recharge. Here you trade off the flexibility of recharge for better energy efficiency on your enchantment duration.
One or sometimes two high-energy sets are also used. This is a wand and/or focus with +15 energy/-1 energy regeneration. Think of this as an emergency pool to fall back on when you're in trouble, but you don't want to stay in it long due to the degeneration. If possible, you want to cast a spell in the high set, then switch back to something else to conserve energy regen. While commonly used by defensive characters, offensive types can also use this to push through a key kill when their energy is out.
As a last note, even casters should use customized staves/wands as that damage is occasionally relevant.
Defensive Sets
Defense sets are common on casters, but they apply just as much to martial characters too, including rangers. Whenever you are taking a fair amount of damage (or better, see that you will be soon), or you are a caster with a warrior on your back, you want to play in defensive set as much as you can. Very good players are expert at swapping weapons while casting a spell, and immediatly swapping back to shield as it finishes, to ensure they have the protection up when they need it against a sudden spike.
A defense set features a one-handed weapon (usually spear) with fortitude and + or - 5 energy. +5 energy gives you flexibility to use skills, while -5 is useful for "energy hiding". E.G. a monk being harrased by energy surge or debilitating shot, can switch into this -5 set to protect their energy. Energy drain skills can't drain below 0 energy, so this protects the pool of energy you have when you switch back to your 40/40 set. Note that sword/axe warriors can stick with their usual weapons, only the shield changes.
For the shield, you're going to have fortitude handle and +10 armor vs <damage type> inscriptions. You'll only have room for one weapon slot most likely, so that means switching the shields around in your inventory depending on the damage type. If lazy you can size up the enemy team near the start of the match and just put the most generally useful shield on: e.g. piercing against dual ranger, blunt if you see a hammer, fire if there are eles around. Good players keep an inventory window open in some corner so they have quick access to thier various shield sets. The additional armor from inscriptions on top of the shield armor just grants the best protection you can get, even if the inscription is only mitigating damage from one or two opposing characters.
In addition to the above, a cripple reduction shield is handy, if you are playing against a team on Burning isle, it will allow you to move much faster through the lava.
Speaking of....
Armor
Survivor insignias are the standard, because they offer the most consistent form of protection. Most +armor mods are conditional, and a balanced spike comes from many different damage sources. While the survivor won't reduce the damage you take, it will provide an extra buffer so that monks have more time to react to spikes. The extra health is also important to help counteract DP, which can accrue from base rezzes in close GvG games.
There are but a few exceptions from the above, and they mostly apply to practically unconditional boosts on high-armor midliners. Most paragons wear centaurion since they always have at least aggressive refrain up. A mesmer with 4+ signets (like the signet smite mesmer) gets +12 unconditional armor from artificers. Both characters sit in shield sets all the time for the extra health and armor, and do so well within range of the monks. But for example +armor while enchanted (or not enchanted) on dervishes is not reliable, because enchant removal (or protting) are common on spikes.
Axe warriors playing Shock may also opt for a few radiant mods, to give them extra energy to play around the exhaustion.
Attribute runes and hat bonus are dictated by your build, all minors (barring sup vigor) except for certain high-armor/self defense stand midliners like paragons and rangers. Any spare spots should go to vitae runes for extra spike protection. Physicals sometimes use a blind/weakness reduction rune, and for rit flaggers w/out condition removal, cripple reduction is useful against the current melandru's/cripshot/caltrops meta.
Finally at the risk of irritating wyrm, I also want to mention hero casters if we need to use them. Without weapon swaps it's a pain to manage them, and easiest if you give them one general set. You also need to compensate for their tendancy for bad positioning and being easy targets for the enemy team. On the typical caster I prefer a +60 HP staff with 20% faster cast on <attribute>. That gives them a decent pool, gives them faster recharges, a cushion against spiking, and maintains their distance better with wanding (vs reduced range of spears). A signet mesmer hero is an exception for having so few spells and high armor from insignias, I'd put them in a defensive shield set.
So a summary of the common equipment configurations:
Martial Weapon: 15>50 of fortitude (or +5 for energy-hungry ranger/sin)
Vampiric and elemental swaps
Sundering for hammers/scythes
Zealous if relevant to build
Condition lengthen Recurve for condition rangers (e.g. cripshot, melshot, apply), vampiric flatbow for attacking NPCs and Read the Wind rangers.
Shields for warrior/para should have fortitude blind, weakness, and cripple reducing sets.
Caster Weapon:
20% half cast time/half recharge on <attribute> wand and focus- possibly two depending on build
40% half cast time <attribute>/20% enchanting staff for enchanting builds
+15 energy/-1 energy regeneration wand and focus, with 20% hct/hr on each, or +30 HP on focus for defensive chars.
Defensive Set:
One-handed martial weapon with +/-5 energy and fortitude
Shields with fortitude and 10 armor vs <damage type>
Cripple reducing shield of fortitude
Armor:
Survivor insignias, sometimes unconditional +armor on non-squishies
Minor attribute runes, superior vigor, viate for rest. Stand ranger/paras sometimes use major.
Blind/weakness reduction on physicals is an option.
Cripple reduction on removal-less rit flagger is desirable.
Hero Casters:
60 HP staff with 20% HCT on <attribute>
Now you should be able to figure out your own equipment templates on builds, but if not ask away!
Martial Weapons
Inscriptions:
+15% damage > 50 HP is near always the preferred choice, because the condition is fairly easy to meet. If you fall below half for any decent length of time, you're probably dead anyway.
A few builds need +5 energy, most notably energy-intensive utility ranger like crippling shot, or some assassin combos. Both of those characters don't lose a whole lot from the extra damage, since Cripshots are all about conditions, and most assassin damage comes from skills. (the 15>50 only affects base weapon damage.)
Suffix: just about always Fortitude. Extra health provides the best protection against spikes and is especially beneficial when you are under DP.
Prefix: this is where things get interesting.
Vampiric is the primary weapon of most melee characters, because the life stealing has the best Damage per Second, and any health loss is usually mopped up by party heals. (often you gain health under vampiric anyway)
An elemental weapon is useful for attacking warriors, who have +20 armor against physical damage. You want to swap into this whenever attacking or spiking a warrior.
Zealous is useful on faster-attacking weapons for some builds, IE generally not hammers/scythes. Warriors can push frenzy more often if they pick up extra energy from zealous. You need to be vigilant about swapping out of it when you aren't attacking to avoid the energy degeneration.
Sundering, everyone's favorite, is only viable for the highest damage of weapons- scythes especially, and borderline for hammers. They have slightly less DPS, but they can randomly make larger spike damage if your critical and sundering chance trigger together. Some prefer that extra random damage for pushing a lucky kill through against strong defenses.
Characters with spammable, short-duration conditions often bring a condition-lengthing mod. A ranger with apply poision typically uses a poison bow, while a cripshot ranger will bring crippling. Warriors with a deep wound on the other hand don't bother, because deep wound is not applied often, and is so dangerous that the opponent should die if it isn't cleaned quickly anyway.
Shields for warriors/paragons always have fortitude mods. The default inscription is usually 20% blind reduction, but you may find switching to weakness or cripple reduction shields useful depending on what the opposing team is using to shut you down. Getting around blind is still the most beneficial if the enemy team has any at all, because blinds are for short durations and may be weathered out instead of being removed.
In addition to the above, rangers need to keep in mind their bow types. For condition-based rangers using apply poison or barbed arrows, recurve bows are favored for their superior flight speed, which makes interrupting much easier. Interrupting in a longbow can be a nightmare if you've tried it. For read-the-wind type rangers, flatbows are common.
While the flatbow normally has terrible flight time and an enormous arc, the extra speed from read the wind negates this, and these prep rangers want both the superior attack speed and distance a flatbow has to offer. Likewise this bow is vampiric so they can do additional direct damage. A short bow should be kept on swap in case Read the Wind is interrupted and disabled for a time, so you can keep up the fast attacks.
Finally, don't forget to customize your pvp weapons on pve characters: the +20% damage bonus is significant.
Caster Weapons:
A 40/40 set or two are the caster's mainstay. (20% faster cast and 20% recharge on (attribute) wand and focus.) You will want this for your one or two main spell attributes on your skillbar. Half recharge gives you much more flexibility on when you can use your skills, and makes your build more efficient if you have the energy. Half cast time is both for efficiency, but it also makes your skills harder to interrupt. Rangers and mesmers can interrupt even 3/4th-second cast skills on reflex, so hitting your half cast time affords some protection against that. It can also help you making a critical save like a heal or blind.
40/enchanting staves benefit a few builds. (20% + 20% faster cast on <attribute>, 20% enchanting, 20% built-in half spell recharge). Such a prot staff is a requirement for using Aegis, lengthing both the critical duration and making the long 2s cast less vulnerable to interrupts. Prot monks spend most of their time in this set, opting for extra enchantment duration over the faster recharge. Here you trade off the flexibility of recharge for better energy efficiency on your enchantment duration.
One or sometimes two high-energy sets are also used. This is a wand and/or focus with +15 energy/-1 energy regeneration. Think of this as an emergency pool to fall back on when you're in trouble, but you don't want to stay in it long due to the degeneration. If possible, you want to cast a spell in the high set, then switch back to something else to conserve energy regen. While commonly used by defensive characters, offensive types can also use this to push through a key kill when their energy is out.
As a last note, even casters should use customized staves/wands as that damage is occasionally relevant.
Defensive Sets
Defense sets are common on casters, but they apply just as much to martial characters too, including rangers. Whenever you are taking a fair amount of damage (or better, see that you will be soon), or you are a caster with a warrior on your back, you want to play in defensive set as much as you can. Very good players are expert at swapping weapons while casting a spell, and immediatly swapping back to shield as it finishes, to ensure they have the protection up when they need it against a sudden spike.
A defense set features a one-handed weapon (usually spear) with fortitude and + or - 5 energy. +5 energy gives you flexibility to use skills, while -5 is useful for "energy hiding". E.G. a monk being harrased by energy surge or debilitating shot, can switch into this -5 set to protect their energy. Energy drain skills can't drain below 0 energy, so this protects the pool of energy you have when you switch back to your 40/40 set. Note that sword/axe warriors can stick with their usual weapons, only the shield changes.
For the shield, you're going to have fortitude handle and +10 armor vs <damage type> inscriptions. You'll only have room for one weapon slot most likely, so that means switching the shields around in your inventory depending on the damage type. If lazy you can size up the enemy team near the start of the match and just put the most generally useful shield on: e.g. piercing against dual ranger, blunt if you see a hammer, fire if there are eles around. Good players keep an inventory window open in some corner so they have quick access to thier various shield sets. The additional armor from inscriptions on top of the shield armor just grants the best protection you can get, even if the inscription is only mitigating damage from one or two opposing characters.
In addition to the above, a cripple reduction shield is handy, if you are playing against a team on Burning isle, it will allow you to move much faster through the lava.
Speaking of....
Armor
Survivor insignias are the standard, because they offer the most consistent form of protection. Most +armor mods are conditional, and a balanced spike comes from many different damage sources. While the survivor won't reduce the damage you take, it will provide an extra buffer so that monks have more time to react to spikes. The extra health is also important to help counteract DP, which can accrue from base rezzes in close GvG games.
There are but a few exceptions from the above, and they mostly apply to practically unconditional boosts on high-armor midliners. Most paragons wear centaurion since they always have at least aggressive refrain up. A mesmer with 4+ signets (like the signet smite mesmer) gets +12 unconditional armor from artificers. Both characters sit in shield sets all the time for the extra health and armor, and do so well within range of the monks. But for example +armor while enchanted (or not enchanted) on dervishes is not reliable, because enchant removal (or protting) are common on spikes.
Axe warriors playing Shock may also opt for a few radiant mods, to give them extra energy to play around the exhaustion.
Attribute runes and hat bonus are dictated by your build, all minors (barring sup vigor) except for certain high-armor/self defense stand midliners like paragons and rangers. Any spare spots should go to vitae runes for extra spike protection. Physicals sometimes use a blind/weakness reduction rune, and for rit flaggers w/out condition removal, cripple reduction is useful against the current melandru's/cripshot/caltrops meta.
Finally at the risk of irritating wyrm, I also want to mention hero casters if we need to use them. Without weapon swaps it's a pain to manage them, and easiest if you give them one general set. You also need to compensate for their tendancy for bad positioning and being easy targets for the enemy team. On the typical caster I prefer a +60 HP staff with 20% faster cast on <attribute>. That gives them a decent pool, gives them faster recharges, a cushion against spiking, and maintains their distance better with wanding (vs reduced range of spears). A signet mesmer hero is an exception for having so few spells and high armor from insignias, I'd put them in a defensive shield set.
So a summary of the common equipment configurations:
Martial Weapon: 15>50 of fortitude (or +5 for energy-hungry ranger/sin)
Vampiric and elemental swaps
Sundering for hammers/scythes
Zealous if relevant to build
Condition lengthen Recurve for condition rangers (e.g. cripshot, melshot, apply), vampiric flatbow for attacking NPCs and Read the Wind rangers.
Shields for warrior/para should have fortitude blind, weakness, and cripple reducing sets.
Caster Weapon:
20% half cast time/half recharge on <attribute> wand and focus- possibly two depending on build
40% half cast time <attribute>/20% enchanting staff for enchanting builds
+15 energy/-1 energy regeneration wand and focus, with 20% hct/hr on each, or +30 HP on focus for defensive chars.
Defensive Set:
One-handed martial weapon with +/-5 energy and fortitude
Shields with fortitude and 10 armor vs <damage type>
Cripple reducing shield of fortitude
Armor:
Survivor insignias, sometimes unconditional +armor on non-squishies
Minor attribute runes, superior vigor, viate for rest. Stand ranger/paras sometimes use major.
Blind/weakness reduction on physicals is an option.
Cripple reduction on removal-less rit flagger is desirable.
Hero Casters:
60 HP staff with 20% HCT on <attribute>
Now you should be able to figure out your own equipment templates on builds, but if not ask away!