Oh, wonderful thread! Here are a few of my own:

classic: first clipless ride. I've been clipping in and out of those darn pedals all the way home as practice, so I feel I have the hang of it but I've obviously got the right one a bit too tight. So next light I coast to a stop, left foot out, hey - I can do this! And timber over to the right, of course.

ugly: I'm 16 years old, and have borrowed a bike too small for me to go to the store to buy ice-cream. I'm on my way back, going around a 90 degree turn, and stand up to pedal. The plastic bag I have hanging off one handlebar swings right into the spokes, the front wheel stops dead and I face-plant into the gravel. I broke both upper front teeth (now root canaled) and bit a sizeable hole in my lower lip.

dorky: coming down a large road at a fairly high speed, lucky, no traffic, music playing on my ear plugs... Cool music, Grease, actually, I start swinging my front wheel in time to the music (honestly, I *never* do this normally). Loud HONK! from a car trying to pass me. Oops, apparently there was some traffic there after all...