Heard a story a while back, probably just an "urban myth", but it could oh so easily be done and turn very nasty.
Student going solo gets into aeroplane and fires her up, wonders why she won't move, realises "chocks are still in", sets throttle at 1200 rpm, forgets to set brakes and climbs out, pulls the chocks out (which must have been f*****g scary being so close to the prop!!), only to find that one brake isn't on and aircraft starts to wheel around, student realises he'll never make it back into the cockpit before the aircraft hits something so grabs hold of the strut. People in nearby clubhouse look out of window and see King Canute trying to hold back the tide and rush to his assistance.
Mayby this story should be published in "My Worst Day" or "I Learned About Flying From That" but I suppose there'd be so many correct entries!!!
Thankfully the worst thing I've personally done is land at a major international airport without landing clearance... and I'll plead the fifth on that one!
Fly safely
BOTR