Please, please, please just make your IM (MSN, Yahoo, AIM, Gtalk) name the same as your own name, okay?
I can't stand looking at my MSN list and seeing a myriad of quotes or 'funny' sayings. When I go to my IM window, I want to see which of my friends are online and find which one I want to talk to. It's such a pain in the ass to double click or hover over a name just to see who it is.
Many clients now feature a comments section, where you can put all your funny quotes and phrases. Please do that and keep your screen name to something that identifies who you are. It would really make me a lot less irritated.