Envious of those colorful emoticons your friends send you from their iPhones? Turn on “Emoji” in iOS 6 or higher by going to the Settings app > General > Keyboard > Keyboards > Add New Keyboard… > Emoji. And now nearly anywhere you can swap your keyboard by tapping the globe button next to the spacebar.
Just note that the only phones that can receive these special characters are iPhone and Windows Phone 7/8. Your Blackberry/Android/dumbphone friends will probably just get generic characters unless they are using a texting app that supports it. OS X Lion or higher and Windows 7 or higher can also display these.
If you have an app to enable emoji you can delete that. Those apps were made obsolete by iOS 6.