Combat Resurrection
A combat res turns a lethal mistake into a timed run. Most groups plan around having at least one battle res in the party.
Specs that bring combat resurrection
Blood Death Knight
Raise Ally
Protection Paladin
Intercession
Restoration Druid
Rebirth
Holy Paladin
Intercession
Frost Death Knight
Raise Ally
Unholy Death Knight
Raise Ally
Feral Druid
Rebirth
Retribution Paladin
Intercession
Balance Druid
Rebirth
Affliction Warlock
Soulstone
Demonology Warlock
Soulstone
Destruction Warlock
Soulstone