These are some cool hidden emoticons in yahoo and please don't mind few are repeating here. But i bet some of them are really not known for most of us. Here are some more emoticons which would surprise your friends.
You can also use a yahoo emoticon assistant (yea) for hidden emoticons and use it for chat. All you have to do is to download a small application for this and install this and and after the setup just open the application and then yahoo chat messenger and select a chat window and send the emoticon by double clicking the icon.