Call of Duty: World at War Cheats

Guardian Angel (Bronze): Kill 3 enemies with a single round.
Gunslinger (Silver): Shoot all of Amsel's henchmen, including their attack dog, without reloading. (Solo only).
Hardened War Hero (Silver): Complete all missions on the Eastern Front on any difficulty. (Solo only).
Hell on Wheels (Bronze): Complete 'Blood and Iron' on Veteran difficulty. (Solo only).
Iron Fist (Silver): Complete a level on Regular difficulty or higher using only melee or grenades. (Solo only).
Kamikaze (Silver): Complete a level using only the flamethrower. (Melee, grenades & explosives are OK).
Lights Out! (Silver): Assassinate General Amsel with a pistol shot. (Solo only).
Mortar-dom (Bronze): Kill 15 enemies while mounted on a tank in 'Ring of Steel'.
No Return (Bronze): Complete 'Ring of Steel' on Veteran difficulty. (Solo only).
No Safe Place (Silver): Collect all Death Cards in the game. (Solo only).
One Bad Gato (Bronze): Complete 'Eviction' on Veteran difficulty. (Solo only).
Platinum (Platinum): Awarded when all other trophies have been unlocked.
Purple Heart (Silver): Complete a level without dying on Hardened or Veteran difficulty. (Solo only).
Rough Economy (Bronze): In 'Black Cats', blast out all of the spot lights in the Japanese cargo convoy. (Solo only).
Ruthless (Silver): Destroy all towers and bunkers in 'Blood and Iron'.
Saved Private Ryan (Gold): Complete the game on any difficulty. (Solo only).
Scorched Earth (Bronze): Complete 'Burn 'em Out' on Veteran difficulty. (Solo only).
Shot in the Dark (Bronze): Kill 8 Japanese with thrown mortars in 'Breaking Point.
Snake in the Grass (Bronze): Survive a banzai attack. (Solo only).
Stabbed in the Heart (Silver): Survive the conflict in Okinawa on any difficulty. (Solo only).
Stormed Peleliu (Silver): Complete 'Semper Fi' on any difficulty. (Solo only).
Sum of All Zeros (Bronze): Kill 10 enemies while the lights are out in the subway in 'Eviction'.
The Hammer Strikes (Bronze): Complete 'Their Land, Their Blood' on Veteran difficulty. (Solo only).
The Last Stand (Silver): Establish a beachhead at Peleliu Island on any difficulty. (Solo only).
The Professional (Bronze): Radio in a naval bombardment that kills at least 4 Japanese soldiers.
The Sun Sets (Bronze): Complete 'Blowtorch and Corkscrew' on Veteran difficulty. (Solo only).
The Sword Is Broken (Bronze): Complete 'Hard Landing' on Veteran difficulty. (Solo only).
Throw a Six and a Half (Bronze): Burn an enemy out of a tree with the flamethrower in 'Hard Landing'.
War Hero (Gold): Complete the game on Hardened or Veteran difficulty. (Solo only).
Weapon of Mass Destruction (Bronze): Save the soldier before he burns to death.

Modes
Complete certain objectives to unlock different game modes.

Veteran mode: Reach Level 32 to unlock Veteran mode, which is a Co-op mode with much tougher enemies.
Zombie mode: Successfully complete Campaign mode to unlock Zombie mode, which is a four-player Co-op mode against endless waves of Nazi zombies.

Multiplayer unlockables
Reach a certain rank on online multiplayer to achieve each unlockable:

Browning M1919: Unlocked at level 61
Clan Tag: Unlocked at level 11
Custom Class Slot 10: Reach Prestige Level Ten
Custom Class Slot 6: Reach Prestige Level One
Custom Class Slot 7: Reach Prestige Level Two
Custom Class Slot 8: Reach Prestige Level Four
Custom Class Slot 9: Reach Prestige Level Seven
Double-Barreled Shotgun: Unlocked at level 29
DP-28: Unlocked at level 13
FG42: Unlocked at level 45
Kar98k: Unlocked at level 41
M1 Garand: Unlocked at level 17
M1A1 Carbine: Unlocked at level 65
MG42: Unlocked at level 33
Mosin-Nagant: Unlocked at level 21
MP40: Unlocked at level 10
PPSh-41: Unlocked at level 53
PTRS-41: Unlocked at level 57
STG-44: Unlocked at level 37
Type 100: Unlocked at level 25