Been playing the shit out of this with Skull, Iron and Kim. Co-Op (or solo) Space Dwarves mining stuff, and fighting waves of enemies (Horde game play a la Gears of War 2, Left 4 Dead).

It has 4 classes (Gunner, Engineer, Driller, Scout) who each have complimentary skills sets, and plenty of stuff to unlock through game play.

Currently on sale on Steam with 25% off