Here’s a quick video overview of a game called WackyLands Boss for the iPhone. I picked this up about a week ago, and so far it’s great. A lot of the game hinges on unlockables and customization, which is great because it gives you an incentive to keep playing.
It’s only $0.99 in the app store, and you’ll get hours of gameplay. I’d give it a solid 8.5; the experience is unique and pretty addicting, but gameplay can get a bit repetitive. Be sure to check it out.