- Broken a bone in a trampoline accident -- because the trampoline fell on me.
It is curious to realize that both times that I have suffered serious injury, it's been within seconds of me asking "what?" instead of paying attention. There's a lesson in there somewhere.
(And it is sobering to realize that, if the same thing happened today, it would probably result in investigation, recrimination and misery. At the time, everyone shrugged, said, "eh -- it's camp", and didn't worry about it much, which strikes me as quite the healthier attitude...)