I'd definetly have to say wrist shot with no backswing.
So I guess a wrist-snap shot.
I just love using that shot, because you keep the goalie guessing where it's going. It's an explosive shot, yet extremely precise..which is probably why I like taking it the most.
My next favorite shot, would be the backhand.
Slapshots would be the last on my list, because I only them it on one timers.