Well, iDoom, anyway. Finally got around to installing iDoom on my 3G iPod, and man, it plays nice. Surprisingly, it's about as snappy as the original game was on the smoking fast 486 DX 66 I played it on back at the Alberta Science Centre...
I was surprised that it doesn't use the scrollwheel to control movement - seems like it would be perfect for steering the little Doomer...
I just checked out the videos of iDoom on various iPods, and man, I need to upgrade to a colour screen version :-)