Ooh i have two.
1. getting kicked in the balls with a footy from about 5 feet away kicked from the hands. I laughed for a split second then dropped like a stone couldn't get up for 2 hours and.. "lost" one of them for a bit
2. I did a Cisse but worse playing football slid to block a shot but didn't see the keeper so the stiker and keeper clashed with my leg in the middle. Safe to say it snapped in half and the bone popped out. 50 odd staples, three screws, one 12 inch and 2 operations later its a bit better. I didn't know much about it at the time though so the first one was probably worse
I have a during video and after photo's lying around somewhere.
Paper cut below gets my vote there horrific..really although losing your balls and kidney stones don't sound too comfertable either.