Personally, blisters from constant roll moves in Street Fighter. But a friend of mine once played Neverwinter Nights for 48 hours straight. He recently had an operation for Crohns, so he didn't eat really, drank very little, and slept in his comfy Adirondack chair. I was talking with him, and he finally stood up to go to the bathroom...and promptly, his legs collapsed under him. It was very baffling. Actually, the same guy got a blood clot from a different Crohns operation while playing with a few friends. Called the Ambulance, and played some Marvel Vs. Capcom while they waited, cause otherwise there was nothing to do but listen to him breath heavily.