The following is a list of perks and their effect:

Tier 1
Flak Jacket: Reduces explosive damageFlak Jacket Pro: Deflect fire damage, and safely toss back grenadesGhost: Undetectable by the Spy Plane and BlackbirdGhost Pro: Undetectable by aircraft, IR scopes, Sentry Guns, and no red cross hair on your name when targetedHardline: Killstreaks require one less killHarline Pro: Change the contents of a Care PackageLightweight: Move fasterLightweight Pro: No fall damageScavenger: Get ammo from fallen enemiesScavenger Pro: Start with extra magazines, and get grenades from fallen enemies
Tier 2
Hardened: Bullets penetrate betterHardened Pro: Increased bullet damage to killstreaks and less aiming recoil when shotScout: Hold breath longerScout Pro: Switch weapons fasterSleight Of Hand: Faster reloadsSleight Of Hand Pro: ADS with all weapons, except sniper riflesSteady Aim: Increased hip-fire accuracySteady Aim Pro: Faster ADS after sprintingWarlord: Equip two attachments to your primary weaponWarlord Pro: Start with one extra lethal and tactical grenade (except Willy Pete)
Tier 3
Hacker: Ability to detect enemy equipment and explosivesHacker Pro: Booby trap enemy Care Packages and turn enemy killstreaks and equipment friendlyMarathon: Longer sprintMarathon Pro: Unlimited durationNinja: Silent movementNinja Pro: Make no noise, and hear all enemies louderSecond Chance: Ability to use your pistol before dyingSecond Chance Pro: Survive longer, and get revived by teammatesTactical Mask: Protects against Nova GasTactical Mask Pro: Reduces the effects of flash and concussion grenades