Perk Slot 1
Marathon | Marathon Pro
Ability: Unlimited sprint.
Pro Ability: Get over obstacles faster.
Sleight of Hand | Sleight of Hand Pro
Ability: Faster reloading.
Pro Ability: Gives a speed boost to how fast you can aim down the sight of your weapon.
Scavenger | Scavenger Pro
Ability: Full resupply from dead enemies.
Pro Ability: Extra magazines.
Bling | Bling Pro
Ability: 2 primary weapon attachments.
Pro Ability: 2 secondary weapon attachments.
One Man Army | One Man Army Pro
Ability: Replaces your secondary weapon. This allows you to change your class at any given time during a match.
Pro Ability: Swaps classes even faster.
Perk Slot 2
Stopping Power | Stopping Power Pro
Ability: Increased bullet damage.
Pro Ability: Increased bullet damage vs. helicopters and aircrafts.
Lightweight | Lightweight Pro
Ability: Move faster.
Pro Ability: Allows you to do a quick aim after sprinting.
Hardline | Hardline Pro
Ability: Killstreaks require 1 less kill.
Pro Ability: Death Streaks require 1 less death.
Cold-Blooded | Cold-Blooded Pro
Ability: Undetectable by UAV, air support, Sentry Guns, and thermal.
Pro Ability: No red crosshair or name shown when you are targeted.
Danger Close | Danger Close Pro
Ability: Increases explosive weapons damage.
Pro Ability: Increases air support damage.
Perk Slot 3
Commando | Commando Pro
Ability: Increased melee distance.
Pro Ability: You don't take any damage from falling.
Steady Aim | Steady Aim Pro
Ability: Increased hip-fire accuracy.
Pro Ability: You can hold your breath for a longer period of time.
Scrambler | Scrambler Pro
Ability: Scrambles (jams) the enemy radar in a small radius.
Pro Ability: Delays enemy Claymores, thus allowing you to avoid the explosion if you are fast enough.
Ninja | Ninja Pro
Ability: Invisible to heartbeat sensors.
Pro Ability: Allows you to move silently.
SitRep | SitRep Pro
Ability: Insertions. This will reveal enemy explosives and Tactical Insertions.
Pro Ability: Makes enemy footsteps louder.
Last Stand | Last Stand Pro
Ability: Allows you to survive a normal death. You will drop to the ground and pull out your pistol.
You can crawl in Last Stand, which was not possible in Call of Duty 4. Last Stand ends after ~10 seconds or if you get shot again, and in both cases, you will die.
Pro Ability: This allows you to use your equipment too, for example, frag grenades and throwing knives.