The Nintendo DS / DS Lite are great game consolle that are really intersting for music production.
Not only chiptune or “gameboy music” but also IDM or very experimental glitch.

The most famous softwares for sale are:

• Korg DS10 : a good sounding combo of two MS10/20 emulators with drum synth (4 drum sounds) plus 16 step pattern sequencer, effects, kaosspads…
  Link to the DS10 website

• NANOLOOP 2.3 : the evolution of the GAMEBOY synth/sequencer with added FM , polyphonic chords…
  Link to Nanoloop 2.3
  

• ELECTROPLANKTON : is a music software that’s a cross between a game and a production tool, because the user interface is game-inspired but the results are really interesting.
  The sw is divided in various “games” that can produce different sounds and process audio signals too.