The COD4 Perks are experience based power ups for multiplayer combat. There are three different types of perks. Perk 1 is the explosive perks, Perk 2 is combat perks, and Perk 3 is the support perks.Cod4 Perks...

1. Perk 1 (blue)
   1. Flash X3 - three special grenades
   2. Bomb squad - find/diffuse enemy bombs
   3. C4 - two C4's
   4. Claymore - similar to C4 except it's a trip mine
   5. RPG-7 - two rocket launcher shots
   6. Special grenades - three more flash/smoke grenades
   7. Frag x 3 - three frag grenades
   8. Bandolier - adds more ammo to clip
2. Perk 2 (red)
   1. Juggernaut - increases health
   2. Sleight of hand - shorter reloading
   3. Stopping power - higher weapon damage
   4. UAV jammer - jams radar
   5. Sonic boom - higher explosive damage
   6. Double tap - faster shooting
   7. Overkill - have two primary weapons
3. Perk 3 (green)
   1. Steady aim - better aiming
   2. Deep impact - better bullet penetration
   3. Dead silence - less noise while moving
   4. Iron lungs - hold breath longer during sniping
   5. Eavesdrop - listen to enemy chat
   6. Last stand - pull out pistol for last-seconds before dieing
   7. Martyrdom - live grenade dropped when killed
   8. Extreme conditioning - sprint longer distances