When playing through Rez on the hardest diff, complete runthrough, without getting hit, multiple times to see how many I could do it...I have severely disabled my ability to use my right thumb the next day from the constant half second fire pulses you have to through the whole game with exact pressure to have the shots count up as fast as possible (PS2). I have also really killed myself playing Ikagura marathons on the DC.
The closest thing to a real injury though would be when playing DDR drunk in the arcade I once slipped and really sprained my ankle.