MSN for business and friends & GTalk for business. I prefer Yahoo's layout most of all and it's compatible with MSN which is nice MSN is a boring tool, no sound smilies no chat rooms but it is most common in business so I have to submit xD. AIM for gaming I guess?? I only rarely use this
Yahoo and SKYPE but on occasion I use Google Talk too. Basically I use anything that can get me to communicate well with people
Digsby with email and facebook notification, with IM protocols like facebook chat, gtalk, aim, wlm, yahoo. I recently removed ICQ protocol due to daily mallware requests.
I use generally a Google talk.But for video conferencing i use Yahoo messenger.Yahoo messenger gives many option during chatting than any other chat messenger.
Skype is really best tool to chat since it has many plug ins for various application like fetching , video recording , snapshot, and desktop sharing