These are the list of emoticons that are allowed in popular messengers:
Yahoo Messenger is one of the earliest messenger service and they are also among the first to integrate smiley in IM. Check out the collection of emoticons from Yahoo Messenger and also the hidden emoticons of Yahoo Messenger.
The best of the uncommon emoticon from Yahoo Messenger is praying 
MSN Messenger
You can check out the MSN collection of emoticons here. The best of the uncommon emoticon from MSN Messenger is Nerd 
GMail and GTalk
There aren’t too many emoticons created by Google in GTalk or GMail. GTalk Emoticons to extend the collection of GTalk emoticons.
AIM Messenger
The AIM Messenger collection of emoticons and the best is the innocent smiley 
, it’s just too innocent.
Yahoo’s EmotiContest
On the note of 25th anniversary of emoticon, Yahoo has announced EmotiContest. They are just about to increase the whole list of emoticons in Yahoo Messenger. All you have to do is take a picture of you with unique expressions and send it to them, which goes for voting and if it goes to the final round they will create a new emoticon based on your expression. These new emoticons will be added later this year to the collection of Yahoo Emoticons.
GTalk Emoticons add-on Not Found!!!