Call of Duty: Modern Warfare 2 Cheats

Homecoming (25): Complete 'Of Their Own Accord', 'Second Sun', and 'Whiskey Hotel' on Veteran Difficulty.
Queen takes Rook (25): Complete 'Loose Ends' and 'The Enemy of My Enemy' on Veteran Difficulty.
Off the Grid (25): Complete 'Just Like Old Times' and 'Endgame' on Veteran Difficulty.
Pit Boss (10): Run The Pit in 'S.S.D.D' and finish with a final time under 30 seconds.
Ghost (10): Plant the C4 in 'Cliffhanger' without alerting or injuring anyone in the blizzard.
Colonel Sanderson (10): Kill 7 chickens in under 10 seconds in 'The Hornet's Nest'.
Gold Star (20): Earn 1 star in Special Ops.
Hotel Bravo (20): Earn 4 stars in Special Ops.
Charlie On Our Six (20): Earn 8 stars in Special Ops.
It Goes to Eleven (20): Earn at least 1 star in 11 different Special Op missions.
Operational Asset (20): Earn all 3 stars in at least 5 different Special Op missions.
Blackjack (20): Earn 21 stars in Special Ops.
Honor Roll (20): Earn at least 1 star in each Special Op mission.
Operative (30): Earn all 3 stars in at least 10 different Special Op missions.
Specialist (30): Earn 30 stars in Special Ops.
Professional (30): Earn all 3 stars in at least 15 different Special Op missions.
Star 69 (90): Earn 69 stars in Special Ops.
Downed but Not Out (10): Kill 4 enemies in a row while downed in Special Ops.
I'm the Juggernaut... (10): Kill a Juggernaut in Special Ops.
Ten plus foot-mobiles (10): Kill at least 10 enemies with one Predator missile in Single Player or Special Ops.
Unnecessary Roughness (10): Use a riot shield to beat down an enemy in Single Player or Special Ops.
Knock-knock (10): Kill 4 enemies with 4 shots during a slow-mo breach in Single Player or Special Ops.
Some Like it Hot (10): Kill 6 enemies in a row using a thermal weapon in Single Player or Special Ops.
Two Birds with One Stone (10): Kill 2 enemies with a single bullet in Single Player or Special Ops.
The Road Less Traveled (10): Collect 22 enemy intel items.
Leave No Stone Unturned (10): Collect 45 enemy intel items.
Drive By (10): Kill 20 enemies in a row while driving a vehicle in Single Player or Special Ops.
The Harder They Fall (10): Kill 2 rappelling enemies in a row before they land on their feet in Single Player or Special Ops.
Desperado (10): Kill 5 enemies in a row using 5 different weapons or attachments in Single Player or Special Ops.
Look Ma Two Hands (10): Kill 10 enemies in a row using akimbo weapons in Single Player or Special Ops.
No Rest For the Wary (10): Knife an enemy without him ever knowing you were there in Single Player or Special Ops.
Three-some (10): Kill at least 3 enemies with a single shot from a grenade launcher in Single Player or Special Ops.

Killstreak Rewards
You can unlock the Killstreaks by receiving the amount designated before dieing.

AC130 Gunship (be the gunner of the AC130): 11 Kills
Attack Helicopter: 07 Kills
Care Package (drops ammo/killstreaks): 04 Kills
Chopper Gunner (be the gunner of the Helicopter): 11 Kills
Counter UAV (jams enemy radar's): 04 Kills
Emergency Airdrop (4 ammo/killstreak drops): 08 Kills
EMP (disables electronics): 15 Kills
Harrier Strike (choose bomb location and defending Harrier): 07 Kills
Nuclear Strike (kills everyone on map): 25 Kills
Pave Low (Armored Helicopter): 09 Kills
Precision Airstrike (drop airstrike): 06 Kills
Predator (guided missles): 05 Kills
Sentry Gun (deployable gun): 05 Kills
UAV (shows enemy location): 03 Kills

Unlock Modern Warfare 2 Museum
The Museum can be selected from the "Mission Select" screen once you've completed the game.

An evening with Infinity Ward: Modern Warfare 2 Gallery Exhibit: Complete the campaign.

Professional Perks Unlocks
With each perk you unlock you can upgrade it by completing various requirements with each one.

Bling Pro (2 Primary Weapon Attachments + 2 Secondary Weapon Attachments): Get 200 Kills with a Weapon with Two Attachments
Cold-Blooded Pro (Undetectable by UAV, air support, sentries, and thermal imaging + No Red Crosshair or Name when you are Targeted): Destroy 40 enemy Killstreak Rewards with Cold-Blooded Perk
Commando Pro (Increased Melee Distance + No Falling Damage): Get 20 Melee Kills using Commando Perk
Danger Close Pro (Increased Explosive Weapon Damage + Extra Air Support Damage): Get 100 Kills with Explosives while using Danger Close Perk
Hardline Pro (Killstreak Rewards require 1 less Kill + Deathstreak Rewards require 1 less Death): Get 40 Killstreaks (2 or more in a row without dying) with Hardline Perk
Last Stand Pro (Pull Out your Pistol before Dying + Use Equipment in Last Stand): Get 20 Kills while in Last Stand
Lightweight Pro (Move Faster + Quick Aim after Sprinting): Run 30 Miles with Lightweight Perk
Marathon Pro (Unlimited Sprint + Climb Obstacles Faster): Run 26 Miles with Marathon Perk
Ninja Pro (Invisible to Heartbeat Sensors + Your footsteps are Silent): Get 50 Close Range Kills using Ninja Perk
One Man Army Pro (Swap Classes at Any Time + Swap Classes Faster): Get 120 Kills using One Man Army
Scavenger Pro (Resupply from Dead Enemies + Extra Mags): Resupply 100 times with Scavenger Perk
Scrambler Pro (Jam Enemy Radar Near you + Delay Enemy Claymore Explosions): Get 50 Close Range Kills using Scrambler Perk
Sitrep Pro (Detect Enemy Explosives and Tactical Insertions + Louder Enemy Footsteps): Destroy 120 Detected Explosives or Tactical Insertions with Sitrep Perk
Sleight of Hand Pro (Faster Reloading + Faster Aiming): Get 120 Kills with Sleight of Hand Perk
Steady Aim Pro (Increased Hip Fire Accuracy + Longer Hold Breath Duration): Get 80 Hip Fire Kills using Steady Aim
Stopping Power Pro (Extra Bullet Damage + Extra Damage to Enemy Vehicles): Get 300 Kills with Stopping Power Perk

Unlockable Multiplayer Weapons and Equipment
Reach the Level indicated to unlock each Weapon and/or Equipment

.44 Magnum (Pistol): Level 26
AA-12 (Shotgun): Level 12
ACR (Assault Rifle): Level 48
AK-47 (Assault Rifle): Level 70
AT4-HS (Grenade Launcher): Level 01
AUG HBAR (LMG): Level 32
Barret .50 Cal (Sniper): Level 04
Blast Shield: Level 19
C4: Level 43
Claymore: Level 31
Desert Eagle (Pistol): Level 62
F2000 (Assault Rifle): Level 60
FAL (Assault Rifle): Level 28
FAMAS (Assault Rifle): Level 01
Frag Grenade: Level 01
Glock 18 (Secondary): Level 22
Intervention (Sniper Rifle): Level 01
Javelin (Grenade Launcher): Level 50
L86 LSW (LMG): Level 01
M1014 (Shotgun): Level 54
M16A4 (Assault Rifle): Level 40
M21 EBR (Sniper Rifle): Level 56
M240 (LMG): Level 52
M4A1 (Rifle): Level 04
M9 (Pistol): Level 46
M93 Raffica (Secondary): Level 38
MG4 (LMG): Level 16
Mini Uzi (SMG): Level 44
MP5K (SMG): Level 04
P90 (SMG): Level 24
PP-2000 (Secondary): Level 01
Ranger (Shotgun): Level 42
RPD (SMG): Level 04
RPG-7 (Grenade Launcher): Level 65
SCAR-H (Assault Rifle): Level 08
Semtex Grenade: Level 01
SPAS-12 (Shotgun): Level 01
Stinger (Grenade Launcher): Level 30
Striker (Shotgun): Level 34
Tactical Insertion: Level 11
TAR-21 (Assault Rifle): Level 20
Throwing Knife: Level 07
Thumper (Grenade Launcher): Level 14
TMP (Secondary): Level 58
UMP .45 (SMG): Level 01
USP .45 (Pistol): Level 01
Vector (SMG): Level 12
WA2000 (Sniper): Level 36
Winchester 1887 (Shotgun): Level 67

Extra Custom Class Slot
Obtain level 70 in multiplayer and enter Prestige mode to unlock a sixth custom class slot.

Extra Custom Class Slot: Obtain level 70 in multiplayer and enter Prestige mode to unlock a sixth custom class slot.

Beat "No Russian" on Veteran Without Playing Level
After beating the "No Russian" level on any difficulty, select it again from the mission menu, this time chossing Veteran. As soon as the level starts, pause the game and it will give you the option to skip the level (due to content). Doing so will skip the level, but will still award you the completion on Veteran difficulty, as though you had played it through to the end.

Bonus Level
Once unlocked, you can access Mile High Club within the Epilogue portion of your Mission Selection.

Mile High Club: Complete the game on any difficulty.