This game has been talked about everywhere but I simply have to link to this. Rolando, a game for the iPhone by ngmoco:), is quite easily the best game for the iPhone or iPod touch (if not the best iPhone application I've ever installed and used).
The gameplay is great. The game has no "controller" interface, as with most well-done iPhone games, but there is an amazing attention to detail in Rolando. If you have an iPhone or iPod touch - this is a game that I highly recommend you buy immediately.