Well I've been mucking about with:

Dungeon Defenders- coop multiplayer, build a base, defend against baddies etc. Worth the sale price but doesn't hit me as a classic

Frozen Synapse- awesome tactical game. It's one that strategy gamers should look up IMHO. There is virtually no luck, nearly 100% tactics as you try to outmanouvre and outhink your opponent's squad. Turn based. A lot of planning resulting in a fist punching the air or a 'oh crap how do I recover from this?' Tense with a decent soundtrack to boot - go look up the youtube reviews.

Gemini Rue- very Phillip K Dick type atmosphere- I'm only an hr or so into this adventure but it's very engrossing so far.