Foo Fighters frontman Dave Grohl is known by many as one of the nicest guys in rock 'n' roll, but we've apparently found what makes Grohl descend into a Hulk-like rage. At the 2011 iTunes Festival, a fan took the band's name a bit too seriously, as he began to fight another concertgoer -- Grohl was not pleased.

"You don't f---ing fight at my show, you a--hole," begins Grohl. "Look at me right here, motherf---er. Look at me. Look at me. Get the f--- out of my show right now! … You don't come to my show and fight, you come to my show and f---ing dance, you a--hole! Get the f--- out of here! I don't put up with that bulls--t. You people come here to have a good time, that guy can f--- off!"