If you like animated gifs like this one, you might enjoy the new Kawaii Emoji iPhone app. With this app you can choose from a plethora of cute gifs and use them in your e-mail or iMessage. The emoticon will be send as an attachment with e-mail and in iMessage it appears as an image inside a balloon (like a photo preview). It would be nice if it was possible to use them for regular messages as well.
The app offeres images which can also be found on Korean websites like Sayclub and Candybar, with characters such as Barunson, Blue Bear and Mashimaro.
Kawaii Emoticons is free, but comes with a banner which you can remove with an in app purchase. Also the four blue sets at the bottom can only be unlocked for €0.89 (per set). All in all even without purchases there are quite some emoticons to choose from.