A good WWII shooter with a good single player campaign and a decent multiplayer component.
The single player part of the game is a decent length and relatively well told. It tells the stories of two soldiers: An American Private, and a Russian soldier. There are a few great levels, and the facts and pictures that show up between levels show a very shocking and mature realism. The single player campaign serves as a fun way of getting used to the WWII weapons in the varied environments of the Pacific and Europe.
The multiplayer is where a lot of time can (and will) be spent. It is almost the same as the multiplayer in Modern Warfare, except for the different weapons and maps. Unfortunately, without the assault rifles and decent sniper rifles, most people rely on the MP40 with a silencer attached and with the Camouflage and Martyrdom perks. This means that the matches aren't as varied as one might hope. When you get a match with people using a wide variety of weapons and perks, there is a lot of enjoyment. The maps are generally good, and the Nazi Zombies mode is a crazy type of survival mode that is extremely fun. The biggest problem with the online is that the other players tend to be incredibly easy to beat most of the time.
Other than a few minor problems with graphics, sounds, and the somewhat annoying multiplayer, Call of Duty: World at War is a solid shooter that is definitely worth trying.
EDIT:
I now have Map Packs 2 and 3.
Map Pack 2: Decent multiplayer maps, but the main attraction is the Nazi Zombies map, Shi No Numa. Shi No Numa is a fun addition to Nazi Zombies and it feels special because of the completely different setting, and the crazy Hellhounds. The Hellhounds shake things up a bit by making the gameplay a little more challenging so that you have to change your tactics to fend off the ravenous beasts before they swarm you. The zombies are also more intelligent and they will kill you a lot faster. Another cool thing about this new Zombies map is that there are actually characters with names and short Bios.
Map Pack 3: The multiplayer maps are fun, but, once again, the main attraction is the Nazi Zombies map, Der Riese. Der Riese is the factory in which the zombies were originally made. There is the new Pack-a-Punch machine, and there are the teleporters that help you make a quick getaway before the zombies ravage you. The Hellhounds are back, but they are less of a challenge because they spawn differently. In Shi No Numa, the dogs would spawn very close to you, giving you little reaction time. Now the dogs spawn in different places around your vicinity. You will generally see the dogs before they see you and begin their charge, allowing you to finish them off rather quickly and easily. This doesn't mean that the map is overly easy, but it does make it a bit less challenging than its predecessor. There are also two great new weapons. The Monkey Bombs are amazing for killing hordes of zombies, or for attracting zombies so that you can Wunderwaffe them into oblivion. The Bowie Knife is also a very useful addition to your arsenal. It is essentially a one-hit kill up until the higher levels.