
ashern |
Pretty much what it says on the tin. I'm trying to come up with abilities that different classes can use to really help buff each other. The thing that for some reason hadn't clicked for me until I started looking around at stuff was Just How Awesome Aura of Justice Paladin ability.
I mean really, at 11th level that's +Paladin's charisma to hit, and +11 damage, per hit, until the enemy is gone, and all of the party members with 30 feet benefit from it! That would absolutely destroy a single boss if the party can focus fire with those kinds of bonuses.
So what other buffs are awesome like that?

GM Arkwright |

It's not a class ability, but it's better than the vast majority of them.
HASTE. hastehastehastehastehasteHASTE.
Haste.
Failing that- Void Wizard's Reveal Weakness to do nasty things to AC and Saves, Cavalier or Inquisitor granting teamwork feats, I'd say a caster summoning monsters counts as it takes much pressure off of party members, witches can Fortune everyone and Cackle all day, Clerics have a few nice auras by that level, Cavalier should have some neat Order abilities and Challenge abilities...

tonyz |

Holy aura and its equivalents. Nice big bonuses (though admittedly you may be able to duplicate them with gear), and the ability to blast outsiders away by discharging the spell.
Spell resistance and (greater) spell immunity. Very handy against magic-using foes, particularly people or creatures with signature abilities.
True sight ends so many problems and deceptions.