I recently tried a little hack using a $.99 iPhone app to enable the cute Japanese Emoji icons on my iPhone. They are definitely a novelty with limited utility as they only show up to other iPhone users, but, if you know other users, they are actually pretty cool. They sure beat Ascii emoticons. There are a ton of the things covering nearly every idea or emotion you could possibly want to convey.
Jailbroken phones have had methods for unlocking them virtually since the Emoji were added to the iPhone, but non-jailbreakers have only recently gotten a couple of somewhat convoluted ways to access them. Here is a new method that looks pretty simple. It uses an iPhone app called Spell Number (iTunes link) that is available for free. It involves entering a specific number into the app to unlock the international keyboards. Hit the link for the entire procedure.