When I've had a hitter, I make a BIG DEAL out of the child whose been hit. I run up and say, "oh noooo, dck, are you ok? You don't like being hit, do you? That wasn't nice. Poor dck, that hurt!" I have totally found (started it with my own kids) that you can evoke sympathy and guilt from the perpetrator by doing this, when otherwise they mightn't give a flying fudge.