Gameboy / Gameboy Colour: The only really successful handheld for years, Nintendo's Gameboy is still going strong today. As well as your bog-standard monochrome effort, there's several multi-platform emulators to play gameboy on, plus SNES and N64 attachments to enhance the experience with 'Super' Gameboy colour graphics. (Although it's interesting, I don't know why you'd really want to.)

Shooter fans are well catered for on the diminutive beastie, with fairly accurate conversions of popular arcade titles such as Nemesis and Parodius, with some original hits of its own...