I do have some game music in my MP3 player (it's not an iPod, it's a Sansa e280 with Rockbox installed). Panzer Dragoon Saga's and Orta's OSTs are there, Halo OSTs, as are songs from The Oneups.
Some stuff from OC Remix has ended up there too, though for the most part, the stuff there sounds like it's just the original with added guitar wailing (the reason why I don't listen to most of The Black Mages or Machinae Supremacy). There are exceptions and remixes by Joshua Morse, for example, have always been quality stuff.
The guy who did the music for Contra IV (Virt [http://virt.vgmix.com]) has some excellent stuff on his site. Usually combines chiptunes with a variety of other things like orchestral and house/techno type beats. Even his plain jane chiptunes are nice.
And like Theo Samaritan, I have a folder full of chiptunes (in various formats: SID, NSF and SPC and a couple others). There's something really interesting about raw chiptunes and the limitations they're done with).