For rooted devices only!

This app will let you conveniently switch out the emoji in your system. Currently available free emoji are Google (stock) Samsung LG and iOS. For a small charge Twitter and Emoji One are also available.

Thanks to gonsa from XDA for providing the font files: http://forum.xda-developers.com/showthread.php?t=2618523

Busybox is recommended and the app is untested without it.