In Call of Duty, the knife is a backup weapon which is nearly always available (with the only exceptions being scripted moments in the campaign or when the user is driving a vehicle or using a mounted gun.
The knife if one, if not the, most powerful weapon in the game. It's quick and easy to use, and can get the player out of a nasty situation if they want to risk it. With the exception of fighting Juggernaghts, and when using custom multiplayer game rules, the knife is a one hit kill. The knife is a one hit-one kill weapon on every multiplayer game mode apart from Old School, where it takes two stabs to kill someone.
Since Call of Duty 4: Modern Warfare, the knife has used two basic animations, a slash and a stab. It is possible to influence which will be used by the direction of player movement. When the player stabs, they lunge forward and the knife penetrates the enemy killing them, but if they miss then the player is open as there is a delay as the character takes the knife back, leaving them open for an attack. When the player slashes with the knife, their arm lashes across the screen and the player can instantly resume control afterwards. Therefore, this slashing animation is more effectiveat very close ranges. In Call of Duty: Modern Warfare 2, there is a Tactical Knife attachment for various pistols, which allows for quicker stabs.
In Modern Warfare 2, there is a Tier 3 perk called Commando which increases the range of the lunge, and improves the knife's lock-on targeting. Many players feel that Commando is overpowered, and the perk was removed in Call of Duty: Black Ops.
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