Lessee... I've put some obscure stuff up on this thread in the past, but maybe I've got some others I haven't mentioned?
Of course, Dan's got me regretting not picking up that Bakshi Wizards game back in the day when I had the chance... ah... youth.
I've got Renegade Legions: Legionairre hanging around. I've been thinking of taking a look at "Better Humans as a theme in RPGs" thanks to this game, actually.
Then there is Marauder 2097, though I'm missing one of the supplements that I used to have. Power armor suits vs formerly human-ish xenomorph types in an anime inspired cyberpunk future Japan... Its actually not a bad little game, and rather interestingly actually lists the methods used to create the book... the layout software and so forth.
Of course I'm gonna keep to stuff that can't really be found anymore, not obscure games currently on the market, like Tenra Bansho Zero and Double Cross, or things that I think were only moderately obscure, like Burning Empires, the Burning Wheel Sci-Fi game... which was much better organized and presented than Burning Wheel.