While single-player games like Witcher 3 and Mass Effect are absolutely amazing, two-player co-op games bring different gameplay dynamics to the table. For instance, both players may share the same end goal, but have different paths to reaching that goal. Keep in mind that we're talking about co-op games, meaning you win together or lose together. The games listed below are specifically designed for at least two players. Vote up what you think are the best co-op games of all time.