Listed here are video game systems that were cancelled before going into production. Most of these systems never made it past mock up stage, and any working units of these systems are usually highly collectable.
Apple Iplay
Action Enterprises Game Master
Atari 2000
Atari 2500
Atari 2700
Atari Cosmos
Atari Game Brain
Atari Mirai
Atari Panther
Atari Jaguar Duo
AT&T 3DO
Bandai HET
Camerica Express
"Eve"
Gamepark XGP
Indrema L600
Konix Multisystem
Nanogear
M2
Phantom
Phillips In2it
Red Jade
Taito Wow Wow
Nintendo SNES CD
Sega VR
Sega Neptune
Ultravision