In MW2 you get three different perks just like MW. However if you use the perks enough then you unlock a “pro” version of the perk which allows you to use the original perk and the pro perk at the same time. I will tell you how to unlock the pro perk in the brackets after the pro perk.
Marathon: Unlimited sprint
Marathon Pro: Climb obstacles faster (Run 26 Miles using Marathon)
Sleight of Hand: Faster reloading
Sleight of Hand Pro: Faster Aiming down the sights (ADS) when stationary. (120 Kills using Sleight of Hand)
Scavenger: Resupply ammo and equipment from Dead Enemies. After you kill someone a blue bag will drop which you walk over to pick resupply. Each bag is equal to one special grenade, one piece of equipment, and one magazine for your primary, 4 mounted shotgun shells, and secondary gun unless you have a launcher, then it’ll be one rocket.
Scavenger Pro: Extra Ammo from the start of your life. (Resupply 100 times while using Scavenger)
Bling: Two primary weapon attachments
Bling Pro: Two secondary weapon attachments (Get 200 Kills using a weapon with two attachments)
One Man Army: Swap Classes while in game. Takes up secondary weapon slot along with perk 1. To use switch to secondary weapon and choose the class you want to switch to. It takes 6 seconds to switch to any of the current custom or premade default classes.
One Man Army Pro: Takes 3 seconds to swap classes. (Get 120 Kills using One Man Army)
Stopping Power: 40% Increased bullet damage
Stopping Power Pro: 40% Extra damage to enemy vehicles (Get 250 Kill using Stopping Power)
Lightweight: Gives a 8-10% Speed Boost when moving depending on your weapon.
Lightweight Pro: Faster aiming down the sights (ADS) from sprinting (Sprint 30 Miles using Lightweight)
Hardline: Kill Streaks require one less kill
Hardline Pro: Death Streaks require one less death (Get 40 Killstreaks while using Hardline)
Cold-Blooded: Undetectable by UAVs, air support, sentries and thermal scope. You will not flash white in the thermal scope and there will not be a red box around you for predator missiles, AC-130, or Chopper Gunner.
Cold-Blooded Pro: No red crosshair or name when targeted (Destroy 40 Enemy Killstreak rewards while using cold blooded)
Danger Close: Increased explosive weapons radius. Explosives are always one hit kill within a certain radius. With this perk the kill radius is bigger by 40% and in turn so is the damage radius.
Danger Close Pro: Extra air support damage by 40% on all airsupport that kills. (Get 100 Kills with explosives while using danger close)
Commando: You can lunge at an enemy to knife them.
Commando Pro: No Fall damage (Get 20 Melee Kills Using Commando)
Steady Aim: Increased hip-fire accuracy
Steady Aim Pro: Longer hold breath duration for sniper scopes. Regular breath is held for about 4 seconds. Steady Aim Pro increases it to about 9 seconds. (Get 80 hip fire kills using Steady Aim)
Scrambler: Jams enemy radar for enemies near you. Stars at 800 MWU radius and completely blocks it in 300 MWU.
Scrambler Pro: Delay enemy’s claymore explosions by 3 seconds. (get 50 Close range kills using Scrambler)
Ninja: Invisible on enemy’s Heartbeat Sensors
Ninja Pro: Your footsteps are silent (Get 50 Close range kills while using Ninja)
SitRep: Detect enemy explosives and Tactical Insertions. They appear as red and can be seen through multiple walls.
SitRep Pro: Louder enemy footsteps by 400% and louder friendly footsteps by 25% (Destroy 120 Enemy Devices using SitRep)
Last Stand: When hurt enough to be killed you fall into last stand where you can shoot enemies until you bleed out (10 Seconds) but you will have 1 Health. Works with all hand guns and the M93 Raffica. If you don’t have any of those as a secondary weapon you’ll pull out a M9 Pistol. You can also speed up your death by killing yourself. To do this hold the reload button (X for Xbox and Square for PS3). If you get headshotted or blown up with last stand on you will not fall into last stand. Instead you will die instantly. Any attachments work on the handguns in last stand including akimbo. If you fall far enough to die, but have last stand, you go into last stand
Last Stand Pro: Use equipment and special grenades in Last Stand (Get 20 Kills while in last stand)