So many things, so many stories.
My first really stupid thing was to dislocate my kneecap, put it back in, get up, dance on it for 3 hours, dislocate it again, put it back in, dance on it for another 2 hours then walk 3 miles home. I was on crutches for 2 months after that (was when I was 15).
Slept with embarrassing girls and ex-girlfriends - kinda standard really.
Got taken into a police station and questioned after I argued with some cop (long story).
Stole 10 'house for sale' signs. Move 5 of them into new houses, so that people woke up with their houses apparently for sale.
Fell off a wall while trying to sneak off with this guy's girlfriend in the dark, couldn't move my neck for the next 3 days and what's worse was that the dude came round the corner and found us about 20 minutes after.
Much much more...