Call of Duty: World at War was my favorite Call of Duty game, though I may go back though and play the others again. Like its predecessors its a first person shooter, but this one is set in World War II’s Pacific theatre and the Eastern front (you play 2 different soldiers). According to Wikipedia, COD: World at War has soemthing new in the series:

A new feature to the Call of Duty series is the co-op mode, which can support up to four players online and two offline.

Also according to Wikipedia this installment has a more mature theme. Heads splat blood and you will see various body parts after explosions – so set the filter if you have young ones.

MORE Call of Duty: World at War LATER..