15Bill Murray vs. Chevy Chase
Chevy Chase has not had a reputation for being a nice guy-- just ask his former Community co-stars. Bill Murray, while being known for having a gentler nature, is no pushover either. There is a reason he gained the nickname "Murricane," after all.
Chase allegedly acted somewhat pretentious when
he returned to the second season of Saturday Night Live to host an episode in 1976. He had left the show to do movies, and the cast reportedly encouraged Murray (Chase's replacement) to confront the funnyman. The fight quickly escalated and fists were thrown. Though the best hit probably came from Murray's verbal insult, as he called Chase "medium-talent."
The fight was broken up by Murray's brother, and the celebs have made up since then. Thank goodness too, because Caddyshack wouldn't have been the same without them. Murray also had a fight with Lucy Liu on the set of Charlies Angels. It is uncertain whether it got physical or not due to conflicting reports. The Murricane indeed.