Voice Fantasy is a weird little app from Square Enix, creators of the Final Fantasy and Dragon Quest series of role-playing games. You may remember Song Summoner, the original RPG created for the iPod a while back (that later came to the iPhone as well). That game had you creating soldiers with songs. Voice Fantasy has you creating heroes with a different audio source: your voice. Just pull up the create-a-hero screen, speak or sing into the iPhone's mic, and the game will create a custom-made hero just for you from whatever auditory groans or screams you can come up with.
Unfortunately, unlike Song Summoner, there's no RPG element to this one. Instead, the game is just a short series of arenas, with your heroes fighting their way up to and defeating the Demon King. You don't actually control the heroes -- they just fight for you, and you can pit them against friends' heroes as well to see whose voice is stronger. If it sounds like a gimmick, it kind of is, but the graphics look great, and the game is just interesting enough to play around with for a while.
There is supposedly more coming, including some characters from a favorite series (perhaps the final part of a fantasy series?). There's also another game mode on the way, and hopefully it's a story mode of some kind, because what's currently there isn't very deep. But it is the latest in a series of interesting experiments by Square Enix on the iPhone, and for US$2.99, it's almost worth supporting just to give the classic game makers a vote of confidence in providing original games for the platform. Voice Fantasy is a strange one, but especially if you're a Square Enix fan, it's worth checking out. And if you're not enticed by this, go get Chaos Rings. That's the full-featured Square Enix RPG for the iPhone that you're looking for.