Cheat List
Cheats in CoD4 are unlocked by collecting the thirty Intel Pieces throughout the game (in the form of laptops). The more of them you collect, the more cheats you will unlock. Here's the list:

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

Easy Intel
The following works on the mission entitled "Hunted". After fighting your way through a basement (after going underneath a bridge, across a field etc), you'll reemerge outside. A nearby house next to a vending machine and a car should be your target from here. Inside the house, there's a laptop on the table. This is a piece of Intel, and collecting all thirty of them in the game will unlock all of the Cheat options available. If you collect the Laptop, and then head through the nearby checkpoint, it will be permanently acquired on your save file. Kill yourself at this point (a Grenade is an easy way to do so), and backtrack to the house. Collect the Laptop again, go to the checkpoint, kill yourself, and repeat the process. By doing this, you can collect thirty laptops without actually collecting all thirty of them.

Arcade Mode
To unlock Arcade Mode, beat the game once through on any difficulty level. Arcade Mode itself is split into two options - Full Challenge or Level Challenge - that add extra replayability to the game.

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.

New Mission
To play an all-new mission, which is an extra mission after the main quest is completed, beat the game and view the ending credits thereafter. After they've run their course, you will then be given the opportunity to play one last single player mission before all is said and done.

Intel Pieces
Below is the level distribution list for Intel Pieces per level, in the form of laptops. If no level is listed, like level 3 for instance, that means that no Intel is available in that mission. Here's the list:

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

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