id Software released an iPhone port of Wolfenstein 3D as open source, besides having its own website, the game that id Software calls "the grandfather of the FPS at your fingertips" is located in the App Store. While the code has been released as open source, the game itself is a relatively high for the App Store $4.99. For those who played the old PC version, you'll have to learn a new control system, as it's been customized for the iPhone (and heck, there's no qwerty keyboard). There are on-screen controls for movement and shooting, but you can also use the motion-sensing abilities of the iPhone to play as well.