This week's episode of The Vampire Diaries, "Memorial", will bring our Salvatore brothers to blows. "Memorial's" trailer spoils a glimpse of Stefan punching Damon, but according to Zap2it, he kind of deserves it.
Damon gets Stefan's fist to his face after telling Stefan something he knows will hurt his feelings. That said, the punch is the end of the fight, not the beginning of it. By the end of the episode, Stefan makes sure Damon is included in an extremely touching gesture.