This tier effects the enemy players equipment (Scrambler/Ninja/Sitrep)and gives players a tactical advantage in combat (Steady Aim/Commando/Last Stand). Unlock Emblem: 500 kills using explosives while using Danger Close.Unlock Pro: 100 kills using explosives while using Danger Close.Danger Close Pro: Increased damage from killstreak rewards.Unlock Emblem: Destroy 250 killstreak rewards using Cold-Blooded.
Unlock Pro: Destroy 40 killstreak rewards using Cold Blooded.Cold-Blooded Pro: No red crosshair or name when targeted.Makes the user invisible to enemy thermal optics, and enemy killstreaks.Unlock Emblem: Get 250 killstreaks while using Hardline.Unlock Pro: Get 40 killstreaks while using Hardline.Hardline Pro: Deathstreaks require 1 less death.Unlock Emblem: Run 250 miles using Lightweight.Unlock Pro: Run 30 miles using Lightweight.Lightweight Pro: Quicker aiming after sprinting.Unlock Emblem: Get 1000 kills using Stopping Power.Unlock Pro: Get 250 kills using Stopping Power.Stopping Power Pro: Increased damage versus vehicles.This Tier deals with the effects on Damage (Stopping Power/Danger Close), Movement (Lightweight) and bonus effects on Killstreaks (Hardline/Cold-Blooded). Unlock Emblem: Get 750 kills using One Man Army.Unlock Pro: Get 120 kills using One Man Army.One Man Army Pro: Faster class switching (from 5 seconds to 3).
However, the effect of the Pro version is granted after respawning. Interestingly, if a Perk Challenge IV is achieved mid-game the "Pro" version will take effect immediately for all classes equipped with that perk. The Overkill perk has been replaced partially by the inclusion of Machine Pistols, Shotguns, and Launchers as secondary weapons and also by the One Man Army and Bling perks. Many of the perks that were in Call of Duty 4 or 5 that are missing are now either part of a Pro perk, available as weapon attachments, or are now deathstreaks, such as Deep Impact (FMJ), Martyrdom and Double Tap (Rapid Fire). These "Pro" versions include the original abilities of the perk, but also add new benefits. In Call of Duty: Modern Warfare 2 the perks are divided into tiers in different way than in Call of Duty 4 and World at War Along with standard perks, players will now be able to unlock improved "Pro" versions of certain perks by fulfilling certain requirements while using them. They affect available equipment, effectiveness of the player's equipment, the usefulness of the enemy's equipment, and the physical properties of the player's character. Perks (referred as Specialties) are multiplayer modifiers in Call of Duty 4: Modern Warfare, Call of Duty: World at War, Call of Duty: Modern Warfare 2, Call of Duty: Black Ops and Call of Duty: Black Ops (Nintendo DS) that passively affect game play, allowing further customization of classes.