I have had a few, but I mostly got away unharmed
1st
riding on some local rocks, went to drop one foot and my chain snapped, I landed with all my weight with my nuts on my stem, spent a little time in hospital, how embarrasing :(
2nd
Riding at tech 04, there was a man made section and one bit we had to gap up to front wheel from a sloped cottol reel up to two stacked on top of each other
Thats me actually doing it a few secs before I fell, as you can see my foot is comming off the pedal, I landed on the reels and put my foot down
Unfortunatly, I lost my balence to my right, I tried to put my right foot down but it was stuck to the pedal.
I fell 6ft onto my back across a curbstone, winded me pretty badly......people said it was the most hardcore crash they ever saw :D
3rd
Riding at the bikeshow this year....
I was making my way up the concrete pillars towards one of the highest parts of the course, I went to gap to the back of the trailor but I had arm pump and my brake slipped, I tryed to rescue it with a dab on the thin metal back of the trailor, but my foot slipped off and I fell 10ft ish on to my back.
I landed on my backwheel though (completley destroying it!), but it took the edge off, so I didnt hurt myself too badly (bruised my ribs)