What's the most little-known and obscure you've ever played?

I'd say Alpha Storm for MS-DOS.
It's a spaceship combat simulator where you control the ship in a top-down view AND an FPS game where you can walk around your ship,defend it against boarding enemies,and even board enemy ships.

Despite being one the best games I've played,all of TAG's other games getting excellent reviews,and also being published by Psygnosis Limited (You know,the guys who made the underrated Colony Wars series),the game is unheard of outside a Mobygames page,a short page on firstpersonshooters.net,and on a couple of shady Russian/Spanish abandonware websites on the web.

Here's a Mobygames page if your interested:
http://www.mobygames.com/game/dos/alpha-storm