A very cool in-browser (no registration required) puzzle game that superficially looks like an X-COM (or Space Hulk) game. Actually, all scenarios are static and there's very little randomness. But it's well designed, has varied and fun missions, and satisfying visuals. Reaction fire is practically unlimited - only by rounds left in the magazine!
The music really kicks ass.
My favourite flash game ever (with possible exception of Samorost, Machinarium etc).