iPhone developer Steven Troughton-Smith has created a very special port of Doom, one that uses the iPhone as touch controller but an external monitor for display. And not any display, but an Apple II's.
Following Erica Sadun's article on how to enable the iPhone's undocumented TV-out features, Troughton-Smith came up with the idea of avoiding the iPhone screen except to draw the controls necessary to navigate through Doom's corridors.