This post is woefully out of date, but I would be remiss if I didn’t mention the single most unique sci-fi tactical miniatures combat game out there:
Gregor Hutton’s 3:16 Carnage Amongst the Stars is a really space-marine-punk RPG. The roleplaying aspects are actually fairly open ended, and the crunch of the rules takes place almost entirely over tactical combat against horrific aliens. The rules are easy to pick up and act as a vehicle for any scene or emotion that the GM and players wish to evoke.
3:16 works fantastic with miniatures, and I highly recommend busting out your sci-fi minis collection and playing a campaign. If you enjoy the free 24-hour draft version for which the Author won a High Ronny Award, you won’t have a problem putting down a few bucks for a glossy color version and supporting exactly this kind of well-conceived indie innovation.