Call of Duty: Modern Warfare 3 Cheats and Tips

Handguns ($250)
LV1 Five Seven Semi-automatic, (single fire)
LV1 USP .45 Semi-automatic, (single fire)
LV2 MP412 Revolver
LV11 Desert Eagle Semi-automatic, (single fire)
LV20 .44 Magnum Revolver
LV40 P99 Semi-automatic, (single fire)
Machine Pistols ($1500)
LV1 G18 Fully automatic, close range
LV3 SKorpion Fully automatic, close range
LV17 MP9 Fully automatic, close range
LV37 FMG9 Fully automatic, close range
Assault Rifles ($3000)
LV1 M4A1 Fully automatic, all purpose weapon
LV1 M16A4 3 round burst
LV5 SCAR-L Fully automatic, all purpose weapon
LV14 ACR 6.8 Fully automatic, all purpose weapon
LV24 AK-47 Fully automatic, all purpose weapon
LV32 FAD Fully automatic, all purpose weapon
LV39 G36C Fully automatic, all purpose weapon
LV43 CM901 Fully automatic, all purpose weapon
LV47 MK14 Semi-automatic, (single fire)
LV50 Type 95 3 round burst
Sub Machine Guns ($2000)
LV1 MP5 Fully automatic, close range
LV4 UMP45 Fully automatic, close range
LV13 MP7 Fully automatic, close range
LV23 PM-9 Fully automatic, close range
LV38 PP90M1 Fully automatic, high fire rate
LV46 P90 Fully automatic, large magazines
Light Machine Guns ($7000)
LV12 M60E4 Fully automatic, large magazines
LV18 PKP Pecheneg Fully automatic, large magazines
LV34 MK46 Fully automatic, large magazines
LV41 L86 LSW Fully automatic, large magazines
LV48 MG36 Fully automatic, large magazines
Sniper Rifles ($2000)
LV7 MSR Bolt action
LV16 Dragunov Semi-automatic, (single fire)
LV29 RSASS Semi-automatic, (single fire)
LV35 L118A Bolt action
LV42 AS50 Semi-automatic, (single fire)
LV49 Barrett .50 Cal Semi-automatic, (single fire)
Shotguns ($2000)
LV1 Model 1887 Lever-action
LV6 USAS 12 Fully automatic, low ammo
LV16 SPAS-12
LV26 KSG -12 Double Barrel
LV33 STRIKER Semi-automatic (single fire)
LV44 AA-12 Fully automatic, low ammo
Weapon Upgrades
LV1 Holographic sight $1000 Holographic sight
LV7 Red dot sight $750 Precision sight.
LV19 Grip $1250 Vertical foregrip for reduced recoil
LV28 M203 Grenade launcher $1500 Undermounted grenade launcher
LV28 GP25 Grenade launcher $1500 Undermounted grenade launcher
LV28 M320 Grenade launcher $1500 Undermounted grenade launcher
LV30 ACOG Scope $1250 Enhanced zoom ACOG scope
LV45 Shotgun attachment $1500 Undermounted shotgun attachment
Equipment
LV1 Frag grenade $750 Refill frags up to 4.
LV1 Flash bang $1000 Refills flash bangs up to 4
LV2 Claymore x5 (10 max) $1000 Directional anti-personnel mine,set off by enemy entering it's proximity
LV3 C4 x5 (10 max) $1500 Charge of plastic explosive,set off manually with detonator
LV27 RPG-7 X2 (4 max) $2000 RPG-7X2
LV10 Body armor $2000 250 armor hit points
LV13 Self revive $4000 When knocked down,shoot your way back up
LV17 Sentry gun $3000 Mini-gun mounted sentry
LV31 Sentry grenade launcher $4000 Grenade launcher mounted sentry
LV37 Riot Shield $3000 Bullet resistant
Air support
LV1 Predators missile $2500 Missile from UACV
LV4 Air strike $2500 Precision air strike on selected location
LV14 Delta squad $3000 Delta force allies drop in via chopper
LV21 Riot shield $5000 Riot shield allies drop in via chopper
LV1 Quick draw $3000 Faster aiming
LV8 Steady aim $3000 Increase hip fire accuracy
LV22 Stalker $4000 Move faster while aiming
LV36 Extreme conditioning $3000 Sprint for longer distances
LV50 Sleight of hand $5000 Faster reloading

3 Kills - UAV
4 Kills - Care Package
5 Kills - Intelligent Munitions System
5 Kills - Predator Missile
5 Kills - Sentry Gun
6 Kills - Precision Airstrike
7 Kills - Attack Helicopter
9 Kills - Strafe Run
9 Kills - AH-6 Overwatch
9 Kills - Reaper
10 Kills - Assault Drone
12 Kills - AC-130
12 Kills - Pave Low
15 Kills - Juggernaut Armor
17 Kills - Osprey Gunner

For the killstreaks and their rewards in Modern Warfare 3, see below:
Assault Strike Package:

3 Kills - UAV
4 Kills - Care Package
5 Kills - Intelligent Munitions System
5 Kills - Predator Missile
5 Kills - Sentry Gun
6 Kills - Precision Airstrike
7 Kills - Attack Helicopter
9 Kills - Strafe Run
9 Kills - AH-6 Overwatch
9 Kills - Reaper
10 Kills - Assault Drone
12 Kills - AC-130
12 Kills - Pave Low
15 Kills - Juggernaut Armor
17 Kills - Osprey Gunner
Support Strike Package:
4 Kills - UAV
5 Kills - Counter-UAV
5 Kills - Ballistic Vests
5 Kills - Airdrop Trap
8 Kills - SAM Turret
10 Kills - Recon Drone
12 Kills - Advanced UAV
12 Kills - Remote Turret
14 Kills - Stealth Bomber
18 Kills - EMP
18 Kills - Juggernaut Recon
18 Kills - Escort Airdrop.
Specialist Strike Package:
Unlock additional perks:
2 Kills - Unlock First Perk
4 Kills - Unlock Second Perk
6 Kills - Unlock Third Perk