I've never injured myself in any hilarious ways, as far as I remember.
My sister, however, is extremely accident prone.
She once broke her collarbone while jumping off of some concrete steps. Another time, she gave herself a labial frenectomy while playing with a broken yardstick. Yet another time, she tried to jump up onto a bed, slipped, and hit her head on the metal frame, which knocked her unconscious. She tore one ACL while playing badminton--another girl was jumping to hit the shuttlecock and one of her feet landed right on my sister's leg. She tore the other ACL while minding her own business, sitting at the base of some bleachers. Two other girls were fighting, and they tumbled down and... landed right on her leg. Those two can't really be considered her fault, but they're still a bit absurd.
I did break my hand punching a bully in the head, when I was a kid. Does that count?