Call of Duty: World at War was one of the best shooters of the year in 2008, but you needed to complete the single-player campaign if you wanted to enjoy the full multiplayer experience.

For instance, the online Nazi Zombie mode has gotten so popular, that new World at War owners are annoyed that they can't participate until they work their way through the single-player campaign. But Treyarch has responded to the complaints, and this weekend, they are opening up the Nazi Zombie Co-Op playlist to everyone on the PlayStation Network and Xbox Live. This mode lets you and up to four other players blast away at "endless waves of – you guessed it – Nazi zombies." In addition, the publisher is also tossing out a crowd favorite: double experience for the weekend! It started yesterday at 1:00 p.m. ET and will continue until "an undisclosed time," although we assume it'll stop some time early Monday morning. Therefore, if you really want to rake in the EXP online, set aside a few hours this weekend. And if you think killing Nazi zombies ever gets old, think again…just about every gamer on the planet gets endless satisfaction out of annihilating the walking dead. Maybe 'cuz they're always so easy to kill, and their bodies to crazy stuff when they die…

Anywho, although we don't expect World at War to be as popular online as Modern Warfare , Treyarch's production is well worth your time. They said they had to produce the best WWII shooter ever in order to live up to expectations and they basically did just that. Kudos.

Related Game(s): Call of Duty: World at War