I’m sure there are more than enough emoticon and Emoji plugins for WordPress, but as I’ve written before rendering Emoji with your own assets comes with copyright problems. Short version: Apple and Microsoft own the copyright to the Emoji artworks in their operating system fonts.
After successfully creating a web font from the Apache-licensed Android Emoji font and spotting the ace Phantom Open Emoji project, I bundled together a WordPress plugin that can display these icon sets to visitors on any system.
Check out the Open Source Emoji plugin on wordpress.org.
There’s work to do as always, but it works! [emoji victory hand]