One method for unlocking secrets in the Wii version of World at War is to achieve a specific number of kills in online multiplayer mode using particular weapons. The number of kills required to unlock bonus items ranges between 25 to150 kills.
Complete 25 kills with the PPSH-41 to unlock the gun's Aperture Sight, which allows for increased aiming accuracy. Get 25 kills with the FG42 to gain access to the gun's bipod, which allows for steadier aiming. 25 kills with the Type 100 will unlock an extended clip, allowing players to carry more ammunition at one time.
Earn 75 kills with the M1A1 Trench Gun to earn a bayonet attachment for the weapon. The same number of kills using the Thompson will unlock its Aperture sight. 75 kills with the Springfield Rifle will earn you its rifle grenade function. Completing 75 kills with the Double Barrel Shotgun will earn you the Sawed-Off Shotgun upgrade, turning the gun into a useful melee weapon.
Achieving 100 kills with the M1 Garand will unlock its grenade launch function, while doing the same with M1A1 Carbine Gun will attach a bayonet to the weapon. Completing 100 kills with either the Gewehr 43 or STG-44 will unlock the telescopic sight on either gun.
As you play "Call of Duty: World at War" online, you'll notice that over time your ranking will go up, which is specified by your Level. Your Level goes up based on a combination of hours played, number of kills and skill level. Reaching Level 2 will unlock the Gas Mask, which protects you from chemical bombs, and the M9A1 Bazooka. Reaching Level 10 unlocks the MP-40 gun, Level 17 earns you the M1 Garand, and getting as high as Level 48 earns you the Fireproof ability, meaning you're character becomes much more resistant to fire damage.