http://ufoai.sourceforge.net/
Squad-based sci-fi strategy.
It's free, but since it doesn't have destructible environments (instead,
you shoot through walls, ugh), I personally won't be playing it. It's just
an old school X-Com principle. I mean, that fence is immovable and indestructible
? C'mon ! Seriously, if any of you know how to help these indie developers
implement ANY kind of destructible environments in the Quake engine, please,
go to their forum and tell them. They went out of their way to refine the
game and make it realistic (wrt weaponry) and very challenging on the medium
to difficult settings.