Ooh, this is my speciality 
When I was 8 I jumped off the sofa while dancing, landed on my back and broke my foot in two place as well as my big toe.
When 12, tripped over an empty coke can on stairs at school and tore the ligaments in the same foot - was in plaster for 4 weeks.
At about 16, got GCSE results and was really pleased, so jumped down the stairs in sheer joy (as I used to do when I was smaller), but had grown a bit so hit my head on the ceiling and knocked myself out.
Since being an "adult" I have:
Given myself a second degree burn on my nipple and breast by ironing without a top on - large, pendulous boobs are dangerous!
Had to have reconstructive surgery on my other foot, total recovery time of a year, after having a water-fight with my husband in the kitchen with laminate floor - I slipped on the wet floor and jammed my foot under the fridge.
Sliced my wrist down to the bone, knicking a nerve and narrowly missing major blood vessels by flushing the toilet. Somehow the handle broke and the remnant sliced straight through, had to have 10 stitches while the doc in A&E was trying not to piss himself laughing.
I could go on...