I love the emoticons in the Gmail web-based IM client. (Are they in the GTalk desktop app as well?)
I’m usually not a fan of graphical emoticons, but these are done right.
They first appear exactly as typed and then rotate upright, which looks cool and is, I imagine, very helpful to any user that doesn’t know about the smiley convention.
I love how the winky icon actually winks, ever so subtly.
It’s nice, by the way, that they’re not implemented as animated GIFs but as background image sprites. This is the winky icon: