Three Tiers of perks with a total of sixteen options are found in Modern Warfare 2. These are Passive rewards that help benefit the player and the play still that is needed to help dominate the game. Each Perk has a Pro option that can be unlocked after completing some challenges.
Perk Tier 1
Marathon
Unlimited sprint.
Pro: Climb obstacles faster.
Unlocked: Default
Slight of Hand
Faster reloading.
Pro: Faster Aiming.
Unlocked: Default
Scavenger
Resupply from dead enemies.
Pro: Extra Mags.
Unlocked: Level 13
Bling
2 primary weapons.
Pro: 2 secondary weapon attachments.
Unlocked: Level 21
One Man Army
Swap classes at any time.
Pro: Swap classes faster.
Unlocked: Level 45
Perk Tier 2
Stopping Power
Increased bullet damage.
Pro: Extra damage vs. enemy vehicles.
Unlocked: Default
Lightweight
Move faster.
Pro: Quick aim after sprinting.
Unlocked: Default
Hardline
Killstreaks require 1 less kill.
Pro: Deathstreaks require 1 less death.
Unlocked: Level 9
Cold-Blooded
Undetectable by UAV, air support, sentries, and thermal.
Pro: No red crosshair or name when targeted.
Unlocked: Level 25
Danger Close
Increased explosive weapon damage.
Pro: Extra air support damage.
Unlocked: Level 33
Perk Tier 3
Commando
Increased melee distance.
Pro: No falling damage.
Unlocked: Default
Steady Aim
Increased hip fire accuracy.
Pro: Longer hold breath duration.
Unlocked: Default
Scrambler
Jam enemy radar near you.
Pro: Delay enemy Claymore explosions.
Unlocked: Level 17
Ninja
Invisible to heartbeat sensors.
Pro: Your footsteps are silent.
Unlocked: Level 29
SitRep
Detect enemy explosives and tactical insertions.
Pro: Louder enemy footsteps.
Unlocked: Level 37
Last Stand
Pull out your pistol before dying.
Pro: Use equipment in last stand.
Unlocked: Level 41