I can't/won't get out of the bath without washing my face three times - though oddly I don't have to do that when I shower.
I will never put on a pair of used socks - I'll even go to the extent of using a pair of my mum's socks (even if there are like trainer-socks on me) if I don't have any clean pairs.
I don't know if it counts, but when I'm out drinking with friends and someone drops a coin in my pint and says "save the queen", I'll always down my pint, even if it means I'll feel/be sick if I do it.
Hmm... yes, those are my main quirks. I may have others but those are the ones that instantly spring to mind.