Overkill

"Carry two primary weapons, no pistol."

- Perk description

Overkill appears as a Tier Two perk in Call of Duty 4: Modern Warfare, Call of Duty: World at War and Call of Duty: Modern Warfare 3, as a Wildcard in Call of Duty: Black Ops II, and appears as an Elite perk in Call of Duty: Ghosts.

Call of Duty 4: Modern Warfare
Overkill is unlocked at level 38 in Call of Duty 4: Modern Warfare. It allows the player to carry a second primary weapon in place of their secondary. When using Overkill, the first primary weapon determines character appearance and movement speed. Perks that affect weapons will affect both primary weapons a player carries, as all perks apply to the player and not their weapons. A player using Overkill will use an M9 during Last Stand.

Call of Duty: World at War
It is unlocked at level 56 in Call of Duty: World at War and has the same effects as in Call of Duty 4: Modern Warfare. When in Second Chance, a player will use a M1911 if they have Overkill equipped.

Call of Duty: Modern Warfare 3
Overkill allows players to carry two primary weapons, as in previous Call of Duty games, though the second primary weapon is incapable of accepting attachments or camouflages, but Proficiencies can still be applied. Overkill Pro allows the use of an attachment and application of camouflage on the second primary. To unlock Overkill Pro, the player must earn 120 kills with their second primary weapon. This perk is featured in the Grenadier default class giving the player a G36C and PP90M1. It is unlocked at level 47, making it the last of the Tier 2 perks unlocked.

This perk can be particularly useful for shotguns, as the secondary weapon can be used at long ranges where a shotgun would not excel due to its range limit. Likewise, a shotgun could be an ideal secondary weapon for another primary weapon (such as a sniper rifle) to be used at close quarter combat where shotguns excel over other weapon types.

The perk can also be seen as more ammunition, due to both weapons having the standard amount of ammo, or full with Scavenger. Scavenger Pro also makes both weapon's ammo count full at spawn. The player is unlikely to run out of both weapons' ammo even without Scavenger, so it is wiser to choose another Tier 1 perk, such as Sleight of Hand Pro to switch to the other weapon faster.

For most weapons, when first switching to the player's secondary weapon, the weapon's switch time is slower, as the first draw animation is the same as picking up the weapon off the ground. It is advisable to switch to the secondary weapon when spawning, and then switch back to the primary weapon, so the player will not have to do the longer switch animation during a firefight, which may cause the player to lose.

Call of Duty: Black Ops II
"Take a primary weapon as your secondary weapon."

- Create-a-Class Description.

Overkill returns as a Wildcard in Call of Duty: Black Ops II.

The second primary weapon may only be equipped with one attachment, unless Secondary Gunfighter is in use (which will give you a maximum of two attachments for that weapon).

If the player intends to carry an Assault Shield as one of their primaries, its a good idea to make it their second primary. This will allow the player to equip two attachments on their other primary without spending a Wildcard (and gives the player the option to equip up to three).

Call of Duty: Ghosts
Overkill returns in Call of Duty: Ghosts as an Elite perk. It allows players to carry two primary weapons. When this perk is equipped, the player may still select a secondary weapon, but a notification will appear, recommending them to take advantage of the perk by selecting a second primary weapon instead.

Trivia

 * If the player is in a private match and the rules are set to no perks, the secondary weapon of any class equipped with Overkill is replaced by an M9 in Call of Duty 4: Modern Warfare, an M1911 in Call of Duty: World at War and a USP .45 in Call of Duty: Modern Warfare 3.
 * It is the only perk not compatible with the Specialist Strike Package, as being given it in the middle of a match would be entirely useless.
 * There are sound files for the acquisition of Overkill when using the Specialist Strike Package, but is never used because of its incompatibility.
 * When Overkill is first applied in Call of Duty 4: Modern Warfare or Call of Duty: Modern Warfare 3, the second primary will be an M4A1.
 * This is the first perk that affects the player's secondary, the second being One Man Army in Call of Duty: Modern Warfare 2.
 * Ironically, despite the perk's effect replacing the player's handgun with another primary weapon, its icons in Call of Duty 4, World at War and Modern Warfar 3 depict pistols.