#3 Portal 2
Portal 2 has as lengthy a multiplayer campaign as its single-player one, casting two players in the roles of Atlas and P-Body With no human subjects left in the Aperture Science facility, GlaDOS creates the aforementioned two robots to perform experiments and participate in tests forever.
Together, two players must cooperate to complete increasingly devious levels that require both players to interact with each other and the environment around them.
The multiplayer mode contains dozens of levels, and once youre through with those, you can download even more levels and player-made puzzles to solve with your partner.
