I was jumping on the trampoline about two years ago. The trampoline just happened to be located at the Karate Studio I frequented (and still do). I was a brown belt at the time, but that is not important.
I was alone on the large trampoline. I tried to invent some new moves on it; I already succeeded doing a kip-up-like maneuver where I landed on my back and sprung forward with my legs down, though they never touched the black membrane below.
I thought, This is cool! Why not do it backwards?
I bounced on the trampoline, gaining momentum. I tried landing on my chest a few times, bouncing precariously high each time. Finally, I landed on my chest for the last time, and sprang backwards, my legs coming up, but as before, never actually touching the trampoline.
However, my torso failed to move. My left knee contacted directly with my nose, which started shooting geysers of blood mere seconds after said incident.
My nose, was of course, broken.
It took about twenty minutes for the bleeding to stop, and for two weeks after, I was unable to participate in kumite (sparring). I still have a small dent in my nose.
The interesting part of the incident was that my sister broke her nose two weeks before, by being savagely butted by a goat.