It's a game that a lot of people complete wrote off when it was announced. You're going BACK to World War 2. No thank you. Wait, there's a 4 player co-op mode? Perhaps. There's also a 4 player co-op mode with zombie Nazis? Ok, sign me up.
With an Xbox 360, PlayStation 3 and PC version there's a Call of Duty for everyone. Each one supports 4 player co-op via the internet or LAN. The console versions also support 2 player co-op via split screen.
There's also a Wii version of the game available this week which supports 2 player co-op. This mode is a bit different as the 2nd player only provides "cover fire" for the main player on a single screen.
Co-Op Articles about Call of Duty: World at War
Hands on Co-Op Preview Zombie Mode: Official Trailer Co-Op Achievements 3D Screenshot