On the topic of mtb crashes, I recall I was at my local bluffs when I decided to have some fun and go off jumps. (As you can see it's not going very well so far)
I was gaining speed and went off the first jump in the trail. While I was just leaving the ground my foot slipped off the pedal and my leg got stuck between the frame and cranks. It caused me to get off balance and flop on my side from a three foot drop. It knocked the wind out of me and bruised my legs pretty bad. I had an indent in my shin for a couple of weeks. It was also embarrassing because I had to sit for a minute trying to get my leg out while all the other people in the vicinity giggled and stared.