If you haven’t played DEFCON yet, you probably should. Can’t go wrong with a 60 megs demo and it’s tons of fun. Well, if you’re into genocide it’s fun (and who isn’t?). It’s from Introversion, the kind folks that made the also quite delicious Uplink a few years back.
If you like it, send them a few bucks. Support basement programming, save the whales, all that.