I stumbled upon this site the other day about handheld devices that are able to play ported versions of the classic first person shooter, Doom.

It turns out the iPod Photo when loaded with a Linux OS can handle playing Doom (although from the video it seems pretty slow).

Still, it looks cool to see Doom on an iPod and maybe in the future they will fix it so that it's not so choppy. Apparently it plays all wad files: Doom I Shareware (won't play demos), Doom II Shareware, Ultimate Doom, Final Doom wads, and my personal favorite Doom II. Check out http://www.ipodlinux.org/Doom for more info, photos, and video.

Disclaimer: I never tried this on my own iPod. For now I'm happy just using the default iPod OS.