Pixel Junk Monsters features a two player Co-Op mode in which players join forces to defend themselves from a constant onslaught of enemies.
One of the unexpected charms of the game is the two-player co-op mode, where both of you have your own currency to spend as you see fit, but can share gems/research. If anything, the game works even better as a multiplayer game, with one of you stationed near the entrance point, and the other keeping guard near the base. Played solo, you're often caught out by your inability to reach parts of the map quick enough, so although you could argue that the game's slightly more challenging solo, it's also less frustrating in co-op, so you takes your choices. The added competitive edge of each having your own score is a nice touch, too.
Read the full review at Eurogamer.