I once managed to get road burn from having someone piggyback me while running at high speed on concrete(yeah i know it's smart), and I slid, cutting a good slice of my leg open, and some of my arm, as well as ripping some skin off my hand. I can still see the healed skin if I look, on my leg and my arm.
I also once pissed a friend off and he made my index finger do a 360 and broke it. Later got it checked out, he'd broken the growth plate in my finger and I had to have a cast for weeks, and have it set.
Speaking of fingers, I nearly got my finger cut off. I got my finger caught in a school door once when I was like, six, and had to get the janitor to help me get out. Later, the janitor told me that I was lucky that they had recently repaired and upgraded the school doors - the old ones had blades in them that would have cut my finger clean off if I had gotten my finger caught in them.
This last one isn't me, but my mother was running once, and she got caught on something and fell(she's p old and has parkinsons, so yeah), and she ended up dislocating her shoulder, and making a gash in her leg, as well as full-on breaking her arm as well.