Since we're discussing favorite abilities, I'd say:
Ventrue: Mass Suicide and Suicide, if there's still someone left
Tremere: Blood Boil, it repaints the area in the color of the enemy's insides
and I enjoyed using it on Johnny at the Glaze
Gangrel: Summon Wolf (or whatever it's called) and that swarm of insects (again, can't remember the name), yet two more things I enjoyed killing Johnny with.