One of the surprise games of the show for me was a little PC title from Stardock and Gas Powered Games called Demigod. I've been loosely following the title for some time, and of course when I saw it had co-op, my interest picked up. The one turn off for me was the fact I thought it was an RTS, something that's not exactly my favorite genre. Turns out, it's anything but.
Demigod is actually something closer to a Diablo than say a Warcraft. Sure the screen is filled with hundreds of troops at a time, but those troops are directly under your control. Instead you control a demigod, and your goal is to turn the tide of the battle by helping those troops. There's a whole RPG meta element over the game as you earn experience for killing enemies and completing objectives. As you level up you'll unlock new abilities and even earn money to use to buy items for your character.