Ziggurat is a fascinating little iPhone game. It's technically a shooter, but the controls are unlike any shooter I've ever seen. The idea is that the human race is almost over, and one lone figher stands atop a pyramid, under attack from robots on all sides. Playing as this solitary fighter, you must destory the incoming robots.
The game offers two methods of firing the weapon: "Precision Mode" and "Slingshot Mode." Precision Mode has you drag a finger across the bottom of the screen to calculate the firing angle, and then tap to charge and fire. In Slingshot Mode, which is easier but less interesting, you simply drag off of the middle of the screen to both aim and charge, as if using an imaginary slingshot on top of the ziggurat.
The enemies vary in size and movement styles, keeping things interesting. Given that every game eventually ends in failure, there's a surprising amount of variety here. The graphics are in a well-done pixel style, and the chiptune music sets a post-apocalyptic mood (with a frightening 8-bit scream when the last human gives up the ghost).
Ziggurat's an interesting bite of a game on the App Store. It's worth the 99 cents just to see how it all works. I don't know that these weird controls would work on any other game for as long, but all of the polish and extra style go a long way in this case.