Perks in general are nothing new to the franchise -- though there are new perks for "Modern Warfare 3." What has changed slightly are killstreaks. Thanks to the new package system, you'll choose either assault, support, or specialist, with each type allowing for particular "strike chains." You can still choose which three you would like to use, should you achieve the necessary kills. The specialist package affords you additional perks, as opposed to a killstreak-like unlock.
PERKS
PERK 1
RECON
SLEIGHT OF HAND
BLIND EYE
EXTREME CONDITIONING
SCAVENGER
PERK 2
QUICKDRAW
BLAST SHIELD
HARDLINE
ASSASSIN
OVERKILL
PERK 3
MARKSMAN
STALKER
SITREP
STEADY AIM
DEAD SILENCE
STRIKE PACKAGES
ASSAULT
UAV – 3 Kills
Care Package – 4 Kills
I.M.S. – 5 Kills
Predator Missile – 5 Kills
Sentry Gun – 5 Kills
Precision Airstrike – 6 Kills
Attack Helicopter – 7 Kills
Strafe Run – 9 Kills
Little Bird Guard – 9 Kills
Reaper – 9 Kills
Assault Drone – 10 Kills
AC130 – 12 Kills
Pave Low – 12 Kills
Juggernaut – 15 Kills
Osprey Gunner – 17 Kills
SUPPORT
UAV – 4 Kills
Counter-UAV – 5 Kills
Ballistic Vests – 5 Kills
Airdrop Trap – 5 Kills
Sam Turret – 8 Kills
Recon Drone – 10 Kills
Advanced UAV – 12 Kills
Remote Turret – 12 Kills
Stealth Bomber – 14 Kills
EMP – 18 Kills
Juggernaut Recon – 18 Kills
Escort Airdrop – 18 Kills
SPECIALIST
Specialist unlocks an additional perk with every two kills, up to eight. If you can pull off eight, you get them all. Awesome.
Recon Pro
Sleight of Hand Pro
Blind Eye Pro
Scavenger
Quickdraw Pro
Blast Shield Pro
Hardline Pro
Assassin Pro
Marksman Pro
Stalker Pro
SitRep Pro
Steady Aim Pro
Dead Silence
DEATH STREAKS
Juiced – 4 Deaths
Revenge – 5 Deaths
Final Stand – 4 Deaths
Martyrdom – 4 Deaths
Dead Man's Hand – 6 Deaths
Hollow Points – 5 Deaths