Yet another good word in for Creeper World 3. Such a great game - this whole conversation makes me want to replay it, actually!
Also, if any of you are into wargames, I highly recommend you try out the Order of Battle: WW2 demo, which contains the training scenarios, which are pretty good themselves. I nabbed two campaigns for it. Looking forward to playing them!
I hear very good things about Atlantic Fleet for $5 being one of the best WW2 naval warfare simulators, even though it appears to be a port from mobile.
Wargame: Red Dragon is also going for $12, if you're into complex, crazy, fast-paced RTS.
Men of War Assault Squad 2 for $7.50 is a steal if you like the game style, as is Age of Wonders 3.
Red Orchestra 2: Heroes of Stalingrad with Rising Storm is going for $5, which, if you like realistic WW2 shooters, it's something you should get.
Also, Cobalt is 66% off. I hear real good things about it, though it's definitely a fast reflexes thing.
Infested Planet is 67% off. It's a really nice tactical game of terran vs zerg, where zerg come at you in literally thousands, and your up to 10 marines need to get upgraded, push hives, etc. Tactical, fun, upgrades. Definitely have a look!
Someone mentioned Distant Star: Revenant Fleet... it felt REALLY meh to me. The battles weren't engaging at all, and were mostly just boring, as you wait for ships to get somewhere, or to finish killing each other. Yawn.