Duke Nukem 3D is now out on the iPhone for USD 2.99 (for one day only). I bought it but personally I wouldn't recommend it to anyone else as the controls are super-sensitive and there's no in-game music.

http://www.joystiq.com/2009/08/11/duke-nuk...iphone-forever/

Also, if you have access to the US iTunes store, Metal Gear Solid Touch is dropping its price from USD 7.99 to USD 2.99 from August 13th till 15th.

http://www.joystiq.com/2009/08/11/solid-sa...ar-solid-touch/

I bought Doom Resurrection on sale as well. It's an on-rails shooter, not a full FPS (you don't control your movement, just your weapon crosshair like Time Crisis etc.). But even so, it's pretty fun and the controls are good. I'm not usually a fan of using the accelerometer for controls, but in this game it's done very well. I would have second thoughts about buying it at the full price (which is USD9.99 I think), but for USD 2.99 I'd definitely recommend it.

The full version of Wolfenstein 3D is also on sale for USD 0.99. Great price as well, and you can try the free version first to see if it's to your liking.

Star Defense has been having several price drops from the original USD 5.99 price over the past few weeks and now it's on sale for USD0.99.

http://stardefense.ngmoco.com/