Cheats are unlocked not by inserting passwords, but by acquiring the thirty Intel Pieces strewn throughout the game. The more of them you collect, the more cheats you can access. On the left are the number of Intel Pieces collected, and on the right are the cheats that are unlocked, with an explanation of what each does.

2 - "CoD Noir" Play the game in black and white.
4 - "Photo-Negative" Game colors become inverted.
6 - "Super Contrast" Game's contrast increases.
8 - "Ragtime Warfare" The game feels like an old silent movie.
10 - "Cluster Bombs" One frag grenade thrown equals five in explosion.
15 - "A Bad Year" Enemies explode into tires when shot.
20 - "Slow-Mo Ability" Game plays at 40% normal speed.
30 - "Infinite Ammo" Just what it says.

Unlockable: Prestige Mode
To unlock Prestige Mode, which is a multiplayer-only mode, you must reach experience level fifty-five. Instead of capping out at level fifty-five, which is the highest level, Prestige Mode allows you to start again from level one. This can be done a total of ten times, giving you ten different icons in in-game lobbies to show your extreme achievement.

Unlockable: Multiplayer Weapons
To unlock the following weapons in multiplayer mode, reach the numbered rank listed.

Assault Rifle (G3) - Rank 25
Assault Rifle (G36C) - Rank 37
Assault Rifle (M14) - Rank 46
Assault Rifle (M4) - Rank 10
Assault Rifle (MP44) - Rank 52
LMG (M60E4) - Rank 19
Pistol (Desert Eagle) - Rank 43
Pistol (Golden Desert Eagle) - Rank 55
Pistol (M1911) - Rank 16
Shotgun (M1014) - Rank 31
SMG (AK-74U) - Rank 28
SMG (Mini Uzi) - Rank 13
SMG (P90) - Rank 40
Sniper Rifle (Barret) - Rank 49
Sniper Rifle (Dragunov) - Rank 22
Sniper Rifle (M40) - Rank 04
Sniper Rifle (R700) - Rank 34

Hint: Intel Pieces
Below is the level distribution list for Intel Pieces, which are enemy laptops full of information strewn throughout the game. There are thirty of them total. The left column is the level in question, while the right column is how many Intel Pieces can be found on that level. Levels with no Intel Pieces are excluded completely.

Level 2 - 2
Level 4 - 2
Level 5 - 3
Level 6 - 2
Level 7 - 2
Level 9 - 3
Level 10 - 2
Level 12 - 2
Level 13 - 3
Level 14 - 2
Level 16 - 2
Level 17 - 1
Level 18 - 2
Level 19 – 2

Submitted by Fi