Some suggestions

Rogue Legacy (This just seems to be right up your alley Day9, and I think its a wonderful idea for you.)

Dungeons of Dredmor (a turn based dungeon crawler with a fantastic sense of humor. Wonderful for anyone really. DO NOT start this on Going Rogue difficulty. You will die. Horribly and often.)

XCOM Enemy unknown (get the expansions, theyre worth it))

Achron (Strategy game. WITH TIME TRAVEL. It can get ludicrously convoluted though)

Risk of Rain (An AMAZING game, both for single player and multiplayer. Although, I would recommend doing it in co-op.)

Space Pirates and Zombie. (Spaceships controlled by you, fast paced battling and a lot of fun.)