Or anyone really. I'm thinking Keef hitting that guy with his Telecaster, John Homme pushing that bloke off the stage. And now, a new one, with a righteous political theme:

http://gawker.com/5991403/dropkick-murphys-singer-kicks-the-crap-out-of-skinhead-doing-nazi-salute-on-stage-during-st-patricks-day-concert

Feel free to share any other incidents here, whether you've been there personally or otherwise.