Headshot

A headshot is a term that describes when a person is shot in the head with a projectile (bullets, arrows, etc.). Because the head contains the brain, which regulates vital body functions like respiration and heart beating, it is the worst part of the body to be shot in in terms of probability of survival. However, the head is a difficult target to hit, and modern militaries train soldiers to aim for the center mass, or torso, for a higher probability of incapacitating a target. This is reflected in Call of Duty in that most deaths are caused by shots to the lower torso.

Call of Duty 4: Modern Warfare
In Call of Duty 4: Modern Warfare, headshots provide a modifier to weapon damage. For the most part, the modifier to a weapon's damage is x1.4. The only exceptions are sniper rifles, which x1.5 multipliers to the head, shotguns, which have 1.0x multipliers to the head, and the M14, which has a 1.5x multiplier to the head. There are also Challenges associated with getting headshot kills, called expert challenges, which unlock special camouflages for weapons.

Call of Duty: World at War
Unlike in Call of Duty 4, headshot multipliers differ. Shotguns have a 1x multiplier, all other weapons excluding unscoped bolt actions have 1.4x, and unscoped bolt actions have 2x. The expert challenges just give experience, not camouflage patterns.

In Call of Duty: World at War's Nazi Zombies mode, headshots can very quickly take out a zombie at any level in two to three shots.

Call of Duty:Modern Warfare 2
Headshots in Modern Warfare 2 work similarly to Call of Duty 4, with the return of gun camo awards. The primary differences are the addition of the Urban and Fall camouflage patterns and the addition of the Prestige Mode Headshot challenges, which in turn unlock additional Callsigns. When a player gets a headshot they are awarded with 50 additional XP, or 500 additional XP in Search and Destroy.