I walk under ladders everytime I see them. And if there are superstitious people around.. I walk backwords back thru it...
I remember ONE chainmail that I actually did. It was the Anti-Chainmail. It stated that if you followed the rules, you'd be immune to all the effect from then on. I figured, a lot of this is crazy, but now I have proof, and I did it.
I can't really think of anything I'm superstitious about.