I loved MSN back in the day. I used it way more than the forums or chat up to 2009. Giant group chats were crazy. I also had a ton of custom emoticons which were the best things ever.

For now, when I IM (which isn't that common), I use Skype. It's okay, I guess, but I don't use it that often and don't talk to very many people on it. There's also Facebook chat but, meh. I prefer IRC these days (though I'm on it less than I used to be).