Lets see...
When i was about 8 I climbed up to the top of a 20 foot tree out in a creek behind our old house. I had done this for months without anything going wrong. I always stepped on strong branches, and never took any risks that high up. This was when I discovered the fact that people are douche bags.
I was sitting up a good 18 feet above the creek. The water was only half a foot high at this point, and below that was rocks. Sharp, uneven rocks. I was sitting on a branch, and my 'friend' though it would be a good idea to take his hand and pull down as hard as he could on the branch I was sitting on. Suffice to say, it broke, I went through a few thick branches that completely snapped under my weight (They failed to slow my rapid descent at all.) before landing on the ground.
Both wrists broken, my nose broken so bad I needed surgery, leg broken in 2 places, sprained neck, my face was bruised for weeks, and I had many, many huge cuts. My screams were kinda loud, as you might imagine, so my parents came running from inside our house. (The tree was in the middle of a forest, they didn't know I climbed it.) Basically I was bed ridden for quite a while, and I kicked my friends ass when I could finally move.