World at War is a game in the Call of Duty series, and features a more mature theme than its previous installments. The game is also open-ended, giving the player multiple ways to complete objectives. The gameplay of World at War shares several features with previous iterations of the franchise. Players fight alongside AI-controlled teammates. They help during the game's missions by providing cover fire, shooting down enemies, and clearing rooms for entry. When playing the Wii version of the game, instead of using a normal controller,such as the ones used by the Xbox 360 and the PlayStation 3, an optional gun-like expansion controller known as the Wii Zapper can be used. The Zapper, or Wii Remote and Nunchuk, can be used to aim at targets to fire at them and simulate marksmanship. The game's return to World War II-era warfare reintroduces weapons and technology that have been seen in other games in the Call of Duty franchise, including the Thompson submachine gun, the M1 Garand Rifle, the Mosin–Nagant rifle, and the Panzerschreck anti-tank rocket launcher. The player gains access to these over the course of the game, but may only carry up to two weapons in addition to hand grenades. Weapons and ammo from fallen foes or friendlies can be picked up to replace weapons in a player's arsenal.
Players can also find weapons with additional attachments, including guns equipped with rifle grenades, telescopic sights, and bayonets. A character can be positioned in one of three stances: standing, crouching, or prone; each affecting the character's rate of movement, accuracy, and stealth. Using cover helps the player avoid enemy fire or recover health after taking significant damage, as there are no armor or health powerups. When the character has taken damage, the edges of the screen glow red and the character's heartbeat increases. If the character stays out of fire, the character can recover. When the character is within the blast radius of a live grenade, a marker indicates the direction of the grenade, helping the player in deciding whether to flee or throw it back at the enemy. The single player campaign includes thirteen hidden "death cards", denoted by playing cards attached to makeshift war graves. There is one in each level (barring those that take place in vehicles); collecting them unlocks cheats for Co-op mode, such as reduced enemy endurance and "paintball mode".