I use Trillian on AIM, ICQ, MSN, Y!. AIM and ICQ are pretty much the same network now since they both use Oscar and can interoperate between themselves. I use mIRC and Xchat depending on where I am for IRC. I tried Skype, but most of my friends aren't half way across the world so thankfully I don't have to talk to my computer. I like the original clients, I just can't run them all at once ... so I used Trillian ... and yes I've probably tried every multi-protocol client out there, but decided on Trillian Pro. I think my favorite all-in-one client was probably yabc. It was really just a jabber client, but right it's too much of a hassle to look for an open and reliable jabber server with the right plugin-ins for external networks. If I had my way, I'd have all my contacts transfer to jabber.