For me, probably this one: http://www.bikeforums.net/classic-vi...rame-gulp.html

You know how sometimes curbs have ramps for wheelchairs/bikes, and sometimes don't? I was absentmindedly riding a sidewalk through my employer's parking lot at night when the latter followed the former, and I flipped in the air after hitting the curb at full speed. The story has a good ending, though -- my noggin was more or less okay, my buddies at the bike shop got to try out their ancient Park Tool frame straightener, and my bike is holding up 2000+ miles later.