I committed many of the acts mentioned here, but the following story wasn't me, honest:
My house-mate at university in Cardiff rode a bike to lectures. He'd taken it home for his dad to fix up one weekend, and they'd removed the front wheel to get it in the car. He put it back together in the kitchen on the Sunday night, but got distracted by the phone ringing.
Come Monday, he set off for lectures. Many students in Cardiff have to pass by the Woodville pub (the Woody to its many friends). If you're cycling, there's a useful shortcut if you hop up over a kerb to get from Senghennydd Road or Woodville Road into Corbett Road, and my mate, approaching the kerb, hoiked up the front of the bike up to do just that.
You can see where this is going... the unsecured front wheel described a graceful arc as it left the fork, bounced a couple of times and then rolled away down the hill towards Corbett Road. My mate took a header over the handlebars of the suddenly-immobile bike, but pulled off a spectacular parachute roll. The drama was improved though, by his satchel coming open and pages of lecture notes blowing all over the place like a sudden snowstorm. This was all at about 8.50 in the morning when the junction was busy with students, including me, on their way to lectures, so there was a significant audience. Most of them - I mean us - were laughing so hard we could hardly help him chase the notes down...