For the past few Co-Op Classics columns, I've been trying to hit some of the key co-op games of the past. Double Dragon and the first Teenage Mutant Ninja Turtles arcade game are on most people's list of classics. Today, we move on to what many consider to be the most influential game ever. This game spawned hundreds of clones, and almost singlehandedly birthed an entire game genre, the first person shooter. A technical marvel, a violent, intense atmosphere, awesome level design and downright scary foes, all wrapped up in a co-op package, make DOOM one of the greatest co-op games of all time.