In Modern Warfare 2 perks are special abilities / power ups for multiplayer combat. There are only 3 perk slots available to you and each slot consist of different types of perks, so choosing the right ones for your class is crucial.
Unlike in the previous Call of Duty games, each perk can now be upgraded to a Pro version by completing its challenge. Note: Pro perks are additions to each perk, they don't replace them. All versions of the game (Xbox 360, PlayStation 3 and PC) unlock the pro perks the same way.
Ability: Unlimited sprint.
Ability: Faster reloading.
Ability: Full resupply from dead enemies.
Ability: 2 primary weapon attachments. This perk has been removed from the COD: Black Ops III perks and moved into a wildcard slot.
Ability: Replaces your secondary weapon. This allows you to change your class at any given time during a match.
Ability: Increased bullet damage. This has been removed from BO2.
Ability: Move faster. Lightweight has been removed from the black ops iii perks list and is available as a Specialist ability.
Ability: Killstreaks require 1 less kill.
Ability: Undetectable by UAV, air support, Sentry Guns, and thermal.
Ability: Increases explosive weapons damage.
Ability: Increased melee distance.
Ability: Increased hip-fire accuracy.
Ability: Scrambles (jams) the enemy radar in a small radius.
Ability: Invisible to heartbeat sensors.
Ability: Insertions. This will reveal enemy explosives and Tactical Insertions.
Ability: Allows you to survive a normal death. You will drop to the ground and pull out your pistol. This perk won't be available in BO2.