I absolutely love Mode 7's tactical shooter Frozen Synapse. Watching your units execute orders that you spent so much time plotting out is incredibly satisfying, even if it goes wrong. When things do go wrong (and trust me, they will), you will always know why. Whenever you lose in a game you need to know why. Otherwise, how will you get better?
Frozen Synapse adds on some new content today, in both the free and "gotta use money" variants. Original Frozen Synapse will get a Hotseat Mode, allowing multiplayer from the same console; Timed Turns, forcing players to make their move quickly (!!!); and Preset Multiplayer Maps, which gets rid of the randomization in favor of fairness in competitive play. All of this will be automatically added to your game, free of charge.
The RED expansion adds, other than the color red, a slew of new features. For $10 you'll get new missions, a new unit, new multiplayer mode, cooperative play, new music, and even more. Between this and the Binding of Isaac expansion, I think I know how my time will be allotted.