Rock of the Dead

Easy achievo just simply use two controllers and select co-op and before the game even loads up the achievo will pop, you dont even have to physical play the co-op game to get it

You can do this with any controller. I used a guitar controller and a regular controller. Pick a level, then a stage. Then with your second controller join and then press the green button (or a) on your first controller. You don't even need to play the stage, as after it loads and shows you the challenges/overview before you start the stage, the achievement automatically unlocks.