I bought a Tapwave Zodiac back in the day and had a blast playing
MAME, Genesis, SNES games.. it could even emulate a PS1 but it was
realllly slow. It also did SCUMMVM text adventure games (Beneath a Steel
Sky, Kings Quest, etc) and was a great movie player.
Battery life eventually blew on it and by then I had migrated over to the PSP.
I hacked mine and have been happy with it. Like earlier posts said the CPS1 and 2
emulators are great, as well as the NeoGeo, Gameboy Advance (laugh -- it
actually plays better than my REAL GBA b/c the screen is better), and so on.
Plus you can play all PS1 games.