Wolfenstein 3D Classic
http://www.idsoftware.com/wolfenstein3dclassic/wolfdevelopment.htm

Developer details the process for putting the full version of the original game on the iPhone

Joy! Wolfenstein 3D has come to the iPhone. I'm playing and loving it. Here's an amazingly detailed article from John Carmack on the design process.

I had been frustrated for over a year with the fact that we didn't have any iPhone development projects going internally at Id. I love my iPhone, and I think the App Store is an extremely important model for the software business. Unfortunately, things have conspired against us being out early on the platform.