Take passives and racials into mind!
Night Elf
Wisp Spirit- Become a wisp when dead with movement speed increase of 50% (25% faster than normal ghost).
Nature Resistance- +10
Quickness- Dodge increased by 1%
Shadowmeld- Activate while immobile and out of combat to enter stealth mode - lasts until canceled - no cool-down. A widely under-rated but nonetheless excellent ability.
Starshards- Rains Starshards down on the enemy target’s head, causing 798 Arcane damage over 6 sec. The spell requires you to channel and is a fine replacement for Mind Flay for those who do not choose the Shadow talent tree.
Elune’s Grace- Reduces ranged damage by 29 at the highest level. Practically never used, and I’m not sure if “ranged” damage includes spells in addition to guns and bows.
Human
Perception- Activate to increase stealth detection radius by 10 yards - lasts 20 sec - 3 min cool down. Useful for fighting those pesky Rogues.
The Human Spirit- 5% increased Spirit. Our primary stat is supposedly spirit.
Diplomacy- 10% bonus to faction point gain. This ability is deceivingly useful. As a Priest, many choose to be a Tailor as one of their trades. Some of the high-level tailoring recipes are only obtained from races which require you to gain faction to trade with.
Sword Specialization- We can’t use swords
Mace Specialization- +5 to Mace skill, although only a minority of Priests use a one-handed mace after level 5.
Feedback- At the highest level, the ability reads Enchants the Priest’s weapon to cause feedback on enemy targets. Each hit has a chance of draining 105 mana from the target. For each mana drained in this way, the target takes 1 damage. Not bad, although outside of soloing, you frequently do not get to melee much at higher levels.
Desperate Prayer- At the highest level, this ability instantly heals the caster for almost 1600. The cool-down is 30 minutes. This spell is widely regarded to be the Human Priest’s defining ability even though it is not unique to them.
Dwarf
Treasure Finding- Activate to see treasure chests on mini map - lasts until canceled - no cool down. Fun!
Frost Resistance- +10
Gun Specialization- No guns either!
Stoneform- While active, grants immunity to Bleed, Poison, and Disease effects. In addition, Armor increases by 5% and speed reduced to 70% of normal. Lasts 20 sec. - 3 min cool-down.
Fear Ward- A buff that prevents a character from fear effects. While a nice ability to have in PvP, it is a massive asset to any raiding guild. One of the keystone fights in Molten Core, Magmadar, is made nearly trivial by this buff.
Desperate Prayer- See Human
Undead
Underwater Breathing- 300% increase in underwater breath
Shadow Resistance- +10
Cannibalize- Increase health regeneration by 200% while consuming a corpse - lasts 15 sec - 3 min cool-down. A nice asset for soloing but mostly for those who cannot heal themselves, ie not Priests.
Will of the Forsaken- Makes yourself immune to fear, charm, and sleep effects for 20 seconds on a 2 minute cool-down. This ability is the cornerstone of the Undead. Priests and Warlocks alike fear this ability as it puts them at a large disadvantage in PvP. Furthermore, the ability can be used while under the effect of fear or sleep which lets you wait until they use their spell before you become immune.
Touch of Weakness- The caster’s next damaging melee attack will cause 64 additional Shadow damage and reduce the melee damage caused by that target by 20 for 2 min.
Devouring Plague- At the highest level this spell reads Afflicts the target with a disease that causes 904 Shadow damage over 24 sec. Damage caused by the Devouring Plague heals the caster. The spell is on a 3 minute cool-down and uses almost 1000 mana which is very relevant at level 60. This spell is a weapon in 1v1 PvP, but it otherwise loses much of its appeal.
Troll
Regeneration - Increases health regeneration by 10% and also works in combat (normal regeneration works off the 5-second rule).
Beast Slaying - 5% damage bonus against beasts. In many ways, this equates to a 5% experience bonus if you choose your hunting grounds with this ability in mind.
Throwing Weapon Specialization - We use wands!
Berserking - Activate when “Wounded” to increase melee and spellcasting speed by 25% - lasts 20 sec - 2 min cool-down. This ability seems good in theory, but in practice you are rarely thinking about it when you are “wounded” which I believe means you are below 20% of your health.
Shadowguard - The caster is surrounded by shadows. When a melee or ranged attacker hits the caster, the attacker will be struck for 116 Shadow damage. Attackers can only be damaged once every few seconds. 3 charges. Lasts 10 min. This spell mimics a Shaman one. It is efficient enough to be used soloing and any extra instant damage in PvP is a good thing.
Hex of Weakness - Reduces melee damage done by a target by 20 at its highest level. Too inefficient at its high mana cost for practical use.
Draenei
Not experienced with a Draenei priest, sorry!
To exr_korn, SPriests have some nice DPS, but Affliction warlocks can throw even more, imo. =)