Not my biggest true fail, but i'll pick the most amusing.
When I was in high school, i'd still occasionally ride a bike around, like to my friend's house, since he lived too close to bother driving but too far to walk. My front wheel would occasionally go a little crooked so that it was rubbing up against the side of that...fork thing. Anyway, I'd just kick it and it'd go back straight. No big deal.
One time we were riding to his house and it happened, and I kicked it, and when I came to my senses an hour and a half later I was standing in his bathroom pouring blood from my face and knees and shoulder and back, with no fucking idea how I got there.
Seems my foot got wedged, I went over the front of the bike, and got myself a nice concussion, and some handy scars as well.
Again, this was in high school. You aren't supposed to "fall off your bike" anymore.