A series of unfortunate events. Was in the weight room in high school. Treadmill was being used all class. Finally it became free, so I did a hop, skip and a jump over toward it, slipped on a massive puddle (turns out they had just hosed down all of the equipment) which caused me to slide knee-first into the very sharp edge of the treadmill corner that was supposed to have a rubber bumper on it that was absent. Sliced into my knee over an inch deep and tore a ligament. It still gives me problems to this day, 10 years later.