Mine involves a little story. I was on a business trip about 6 years ago, and took some customers out to dinner. Nice place, but not super expensive since I didn't want to give them the impression we were making tons of money off them. Anyway, we had some good food and good conversation. The only odd thing was that they all drank iced tea and I had 2-3 beers.
So, I get back to the office a couple days later and start catching up with my email. I get to one from a co-worker of mine who enclosed a large version of my avatar pic. Apparently the customers I took out to dinner were rather strict Mormons and long story short, several folks from our company had to profusely apologize for my behavior.
I use it as my avatar to remind me how much I indeed suck.