Aim/ym
Im usually on AIM at work, but if I have to switch screens, I will go to YM.
I dont have a computer set up at home yet, so can't use either then...my parents wont allow it on their computers. And I respect that.
I guess when I get my computer online at home, I will just use AIM and YM as I cannot stand MSN or ICQ...they have messed up so much, so often, when people ask me to download them, I tell them I prefer not to, and that I'm on AIM or YM, and if not, they can email me.
Smiles!