The singer of The Hope Conspiracy apparently hurt several people at the show I was at (some were bleeding from their face, one looked like his nose was broken or something, I don't know) and he also hit equipment (lighting and stuff) with his microphone. But I'm not quite sure whether those were accidents. ... Coming to think of it, I think he did all of that on purpose.
One of North of America's guitar players' contact lenses suddenly slipped during a song and apparenly really hurt his eyes. But he couldn't stop playing, so at the end of the song, he was crying (well, tears were coming from his eyes because of the irritation the contact lenses caused). Then they dropped to the floor and he had to play the rest of the show blindly (his glasses had been lost in accident earlier on when their tour bus had caught fire).
Then, at the same show, two guitar straps simply fell apart which also caused mayhem.