Secondary Weapon

Secondary Weapons are weapons that take up the secondary weapon slot in the inventory. Originally, secondary weapons provided players with the ability to quickly swap weapons in case one ran out of ammo, but recent installments give the player more flexibility in customizing their class to fulfill more roles in combat.

Call of Duty and Call of Duty: United Offensive permitted the player to carry two primary weapons and a pistol sidearm. Beginning with Call of Duty 2, players could only carry two weapons of any kind. Modern Warfare 2 expanded the secondary weapon slot to include a great range of weapons, including:
 * Launchers, such as the RPG-7 or AT4
 * Shotguns
 * Handguns
 * Machine Pistols

The One Man Army perk takes up the secondary weapon slot.

To use the secondary, the player simply has to swap from the primary weapon using the Swap Weapons button. The speed of the swap ranges from each classification of Secondary Weapon, Pistols being the fastest and Launchers being the slowest. Each Secondary also has its own amount of Attachments (excluding Launchers) and usage, such as the G18 being used in typical Sniper Classes in case an unwelcome guest decides to attempt an ambush, or the AA-12 can be used to quickly make haste and wipe a room out to capture an objective.

Secondary weapons do not have challenges that require other attachments, like getting the Holographic Sight from sixty Red Dot Sight kills, nor do they have mastery. This makes them a little less useful when wanting to get experience, but they are still very useful.

Overview

 * Pistols can be used as a quick finisher as these Secondaries have the fastest swap time out of the four Secondary Weapon groups.
 * Machine Pistols are frequently used in Close Quarters Combat to midrange, as they have high damage or rate of fire but limited range and high recoil.
 * Shotguns are used as a quick blow to enemies at close range, and even earn Double to Multi-kills, as it's tough to survive a blow from a Striker or SPAS-12 without the aid of the Deathstreak Painkiller.
 * Launchers are either a type of Splash Damage Secondary, or an Anti-Air Secondary; The RPG-7, AT-4, and Thumper make use of a large explosive radius while the Stinger and Javelin are the Anti-Air Launchers (the Javelin is also capable of locking onto ground targets albeit taking longer to get there than the RPG-7 and Thumper).
 * Secondary weapons can not accept Weapon camouflage in multiplayer.
 * Swapping to a secondary doesn't increase movement speed, so if you want to use a weapon such as a USP .45 with Tactical Knife for speed knifing, it is suggested to use a high maneuverability Primary Weapon, such as an SMG.

Tips

 * The Perk Last Stand only allows the use of Pistols and in Modern Warfare 2, and the M93 Raffica. If a player goes into Last Stand with any other secondary weapon, they will pull out an M9, or an M1911 in World at War.
 * All Secondary Weapons, excluding Launchers, may be equipped with an attachment, or two with Bling Pro.
 * There are situations in which secondary weapons are more effective than primary weapons, leading players to sometimes rely more on their secondaries.
 * Some Secondaries, such as the PP2000 and the Model 1887, need to be "primed" when first taken out. Try to make a habit of always switching to your Secondaries and back when you respawn.
 * When using a machine gun in Modern Warfare 2, it is highly advised to equip a pistol, if caught reloading.