The ones that you've never forgotten/lived down? The ones that make you cringe when you remember it?
I remember crossing the road, I was about 8 and was waiting in the middle when a bus stopped to let me cross. I gave him a cheesy smile and a thumbs up as I got to the other side, however, due to me not looking where I was going, i tripped on the kerb and went flying, skidding across the floor and landing in a heap. Instead of just running off and crying in my room, I turned back to show I was okay (with another thumbs up - damn I'm an idiot!) - the full bus was laughing at me 
Still makes me red just thinking about it.
Anyone want to share? I love a good cringe story 