OK, it's going to be hard to top hanging yourself from a fence, but I've got a couple of items for you.
Back in the baby days, I was blessed with a baby that never slept more than 2 hours at a time. By the time she was six months old, I had become a sleep deprived idiot. So one day (or night, who can tell at that point?) I wake up to incredible screaming. This kid was obviously ticked off. When I get to her room, I look down and see that she is COVERED in p##p. I'm thinking she must have some sort of a tummy issue so I pick her up and head toward the tub. When I strip her down, I find out she is not wearing a diaper at all. I'm guessing I forgot a step in the process the time before when I got up with her.
This one is my Aunt's stupid moment. (Refer to the "Redneck" thread for reference to said Aunt) Before they got indoor plumbing (1979) she cozied up to the woodstove before heading to the outhouse. This aunt has always been a fancy pants kind of lady so her outhouse had a real toilet seat instead of just a plain wooden hole. (It was also a two holer with a tall hole and a short hole. See how uppity she is?) Anyway, after getting her behind all sweaty warm on the woodstove and then setting on the cold plastic toilet seat, she froze to it! Just like licking a flag pole! She yelled for help and the entire family went out to see what was up. The poor woman is still teased at every family gathering.