Xbox Live Unlockables
[Submitted by: Cheat Masters ]
If you have a pair of Xbox Live accounts, you can try this technique. If one account is of a lower rank than the other, you can give the lower account an instant power-up when using both accounts to play. When you unlock something at the end of the game (such as the Overkill Perk), immediately log out of your account and sign into the lesser account. Head to the Xbox Live game lobby and press Y, and the game will have unlocked for this particular account whatever you unlocked with the first account.

Intel Pieces
Below is the level distribution list for Intel Pieces!
Intel Pieces are enemy laptops full of information found throughout the game. There are 30 of them total.

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

Multiplayer Weapons
Description: 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

Arcade Mode
Description: Arcade Mode itself is split into two options - Full Challenge or Level Challenge - they basically add extra replayability to the game.
How to unlock: Beat the game once through on any difficulty level.

Cheat List
Cheats are not unlocked by inserting cheat codes! They are unlocked by acquiring Intel Pieces. Intel Pieces are enemy laptops full of information found throughout the game. The more of them you collect, the more cheats you can access.

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

Prestige Mode
How to unlock Prestige Mode: (multiplayer-only mode) you must reach experience level 55. 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 10 times, giving you 10 different icons in in-game lobbies to show your extreme achievement.

Golden Weapons
Description: Unlock the following "Golden" weapons, fulfill the requirement listed.

AK-47	Complete all Assault Rifle challenges
Desert Eagle	Attain Level 55
Dragonuv	Complete all Sniper Rifle challenges
M1014	Complete all Shotgun challenges
M60	Complete all LMG challenges
Mini-Uzi	Complete all SMG challenges

New Mission
Description: Play an extra mission after the main quest is completed,
How to unlock: Beat the game and view the ending credits. Then you will be able to play one last single player mission.