Killstreak

A Killstreak is earned when a player acquires a certain amount of kills in a row without dying.

In the multiplayer modes of Call of Duty 4: Modern Warfare, Call of Duty: World at War, Call of Duty: Modern Warfare 2, and Call of Duty: Black Ops, the player is given various rewards depending on how long the killstreak lasts. Most killstreaks provide air support, but some, like the UAV, SR-71 Blackbird and the EMP can help the user's entire team by giving or blocking radar.

Call of Duty 4: Modern Warfare

 * 3 Kills - Radar: Deploys a UAV to scan the maps for 30 seconds and reveal enemy locations. Enemies with the second tier perk UAV Jammer will not be detected by the UAV.
 * 5 Kills - Airstrike: Call in an airstrike on a targeted area of the map.
 * 7 Kills - Helicopter: Deploys an attack helicopter, either an AH-1 Cobra or Mi-24 Hind (depending on what team the player is on), to engage enemy players for one minute. It can be shot down with RPGs, launched grenades, or concentrated gun fire.

Call of Duty: World at War

 * 3 Kills - Recon Plane: Deploys a recon plane to scan the map for 30 seconds and reveal enemy locations. Enemies with the second tier perk Camouflage will not be detected.
 * 5 Kills - Artillery: Calls in eight artillery shells to strike a designated location. Player will experience shellshock if close to where the shells are landing.
 * 7 Kills - Dogs: Calls in a pack of vicious dogs for one minute time. If dogs are killed, more spawn. Friendly dogs appear as tan and black German Shepherds, enemy dogs appear as solid black German Shepherds.

Call of Duty: Modern Warfare 2
In Modern Warfare 2, players can choose up to three killstreak rewards they can earn, rather than just the standard three. At the start, the player can only use UAV, Care Package and Predator Missile, with the option to unlock one new killstreak at each of the following levels: 10, 15, 23, 35, 47, 51, 55, 59, 63, 66, 68 and 69 (all killstreak rewards will be unlocked at level 69). When a killstreak of 8 or more is activated, a message will notify all players in the match, showing the callsign and the streak being used (except in Hardcore or when the killstreak is a Stealth Bomber being deployed by the opposing team). Even though a Tactical Nuke is announced to both teams, the player's callsign on the top-right corner will only be shown to players on that player's team.

It is worth noting that two killstreaks that share the same killstreak amount cannot be used together, one must be picked over the other. For example, for the 7 kills slot the player can use either the Harrier Strike or the Attack Helicopter, but not both, as well with 9 kills slot the player can use either the Pave Low or the Stealth Bomber and the 11 kills slot the player can choose from either the AC-130 or the Chopper Gunner.

For controllable killstreaks (Predator Missile, Chopper Gunner and AC130), if the player is killed while operating the killstreak, the player can continue using the killstreak until it is done and then respawn or enter spectator mode as normal. The only exception to this is Search and Destroy.

Call of Duty: Black Ops


Black Ops features a similar customizable killstreak reward system to Modern Warfare 2. All killstreak rewards are available for purchase, via CoD Points, at rank 10. Kills from killstreak rewards don't count towards higher killstreaks unlike previous titles, which means that players must kill the required number of enemies themselves. Also, the Tactical Nuke has been removed.

If caught as it approaches, the helicopter dropping the reward crate may be shot down and the killstreak reward lost by the opposing team.

Trivia

 * W00t killstreakz.png In Call of Duty 4: Modern Warfare and Call of Duty: World at War, killstreaks do not stack (ie, if a player does not use a Killstreak when they get another one, the first Killstreak is lost). In Call of Duty: Modern Warfare 2 and [[Call of Duty: Black Ops]] they stack with the most recently rewards earned being first in the queue.
 * In Call of Duty: Modern Warfare 2, if Predator Missiles from both the enemy team and the friendly team are in the same place, the icon in the minimap will be shown as yellow.
 * In Call of Duty: World at War, there originally was a Fourth Killstreak.
 * In Call of Duty: Modern Warfare 2, killstreaks were originally divided into categories and players could select up to three of them.
 * In Call of Duty: Modern Warfare 2, the UAV, Counter UAV and EMP are the only killstreaks that do not directly kill enemy players.
 * In Call of Duty: Modern Warfare 2 there are chatter sounds for a Little Bird killstreaks. However, these killstreaks are cut from final game. Also, chatter sounds for enemy Predator Missile, Sentry Gun and Airstrike can be found in game files, but they're not used.
 * The Valkyrie rockets, Chopper gunner and Gunship are not included in the Wii version of Black Ops.
 * In Call of Duty: Modern Warfare 2, if one switches teams on a private match after having earned a killstreak without using the killstreak first, the player will lose the killstreak.
 * Killstreaks are still destructible after a match ends, meaning if the player fires a rocket or AC130 guns at an enemy aircraft, one can still get points if the match ends before the rocket/round hits.
 * In Call of Duty: Modern Warfare 2, there's another killstreak called "Tank" - An image of a rank, In the Compass (radar) can be found. Also, a script file of _tank.gsc killstreak can be found too.
 * In the Modern Warfare 2 Official Strategy Guide, in the Multiplayer section, there is a picture of a Tactical Nuke referred to as "Nuclear Strike", with a photo of a mushroom cloud instead of a radiation logo. In that same picture, the Predator Missile goes by the name "Hellfire".