First time I ever got on a motorized two-wheeler I dumped the clutch and stalled it. I was like 15yo, didn't end up on my ass but was still kind of embarassed. The bike was was my friends very cute sister's Honda 125. I (they) picked me up and I rode all the way to Greentown and back that day, I wasn't trying to race so I just let off the throttle to shift and it was fine.
Second time I rode was a Maico 400 2-stroke, I took it around the block. That beast would have run to 50mph in first gear. People in my neighborhood were nuts for even letting me try these monster machines. :)
I tried a Suzu 80cc for about 30ft one time and hit a phone box thing...STOP - went flying over the handlebars.