Take to the skies as you fight to dominate the air. Extremely intense player vs. player action as 4-man crews command flying war machines.

Awesome 2-player co-op that offers more content than the actual story mode. Disclaimer: Requires thinking with portals.

Best co-op heist game of all time. Runs fluidly from ninja-esque robbery to comedic botch-job and manages to be fun all the way. Great soundtrack too.

The online community has died out, but if you can find another player (or convince a friend to buy it), it becomes a fantastic co-op beat 'em up.

While it works best with friends to play with in person, Keep Talking is one of the best casual party games around.

Incredibly deep roguelike. Tons of items to play around with. Afterbirth DLC takes it to another level in almost every area and a new mode to enjoy.

Duh.