Flour said:
Phantasy Star Online Episode 1&2 was also very rare. It is one of the few gamecube games that can actually be played online, the name and packaging implied it was online-only and again, I was very lucky to have found my copy because the game was no longer produced and I found one of the last copies.
I have it, and I bought a gamecube modem just for it.
I also have the Dreamcast version of PSO Version 2. (basically episode 1 with another difficulty to grind, and another 100 levels to grind as well.)
That one I've played online. The GC one, I never got around to it because I couldn't find a broadband adapter in stores...
And, uhh, since I can't think of anything, I'll go with Corncob 3D here, or Jill of the Jungle, or maybe I should start naming things people have heard of, like Ikaruga or Shenmue or something.
I know! I'll do rarest per console!
Odyssey 2: (The console itself, perhaps.)
Sega Genesis: Sunset Riders I think, maybe Asterix is rarer.
Sega Saturn: Fighters Megamix 2 (Most are mainstream games :/)
Atari Jaguar: (
N64: Turok: Rage Wars or Excitebike 64 (Mostly mainstream games)
Sega Dreamcast: Evolution 2: Far Off Promise
Gamecube: Ikaruga (I think, anyway, though that Robotech game and Hunter: The Reckoning I've never seen other than where I bought them...)
PC: Too many to list.