AT4

The AT4 is a launcher featured in Call of Duty 4: Modern Warfare and Call of Duty: Modern Warfare 2, but was cut from Call of Duty: Modern Warfare 3.

Campaign
The AT4 is seen strapped to the backs of some USMC members, but is only usable by cheats. The only time it is seen being used is in "Shock and Awe" and "All In". It is seen in Shock And Awe when a soldier pulls it out and fires it at a cluster of buildings. It is seen again in All In when a S.A.S. soldier fires it a chopper. The last time the AT4 is seen being used is when the player reaches the top of the under-construction building; one of the besieged troops will fire it into a crowd of troops right before the player gets to the top.

The AT4 can be used on the levels "Shock and Awe" and "Game Over" by enabling the "give all" or "give at4" cheat (this will only work on the PC version). The weapon, which is normally dropped by NPC's after firing, has no reloading animation. So when it is fired by using the cheat, it is just suddenly reloaded and ready to fire again.

Multiplayer
In multiplayer, the AT4 was originally supposed to be given to the player as a first tier perk. The perk's icon still remains in the game files, along with a kill picture which was used in Call of Duty: Modern Warfare 2. It was probably replaced by the RPG x2 perk.

Call of Duty: Modern Warfare 2
The AT4 debuts as a usable weapon in Call of Duty: Modern Warfare 2. This version is called the AT4-HS (Heat-Seeking Launcher) as it is capable of locking on to aircraft. To lock-on, the weapon must be ADS aimed at a aircraft until a clear, loud tone is heard and then fired.

Campaign
The AT4 can be seen and used during "The Only Easy Day... Was Yesterday", "Of Their Own Accord", and "Just Like Old Times". It is referred to in the pickup prompt as simply "AT4," and is only capable of free-fire in the Campaign mode. In "The Only Easy Day... Was Yesterday", the AT4 can be found before the player breaches the second room, and also inside the second breach point itself. A third AT4 can be found in the hallway near where the helicopter attacks the team. In "Of Their Own Accord", it can be found on a table next to the pile of bodies near to the entrance of the bunker the player spawns in. In "Just Like Old Times," the AT4 can be found in a few places such as outside the explosive-rigged control room and in the yard before the boat chase.

Multiplayer
This AT4 is the first rocket launcher to be unlocked, at level four, and is also part of one of the default classes. Unlike in the campaign, the player does not discard the apparatus after firing the rocket. It is capable of both free-fire and lock-on, although it does not do as much damage as the Stinger or Javelin to any aircraft. It does the same amount of damage as the RPG-7 against infantry, although with a smaller blast radius and only one rocket. However, it is far more accurate, especially at range, and can be lock-on fired. Like the others, however, the player must be aiming down the sights in order to fire.

AT4's can be useful in taking down helicopters with flares so long as the player has Scavenger. The player simply has to fire an unguided rocket at a helicopter without locking on, which means there are no flares. However, this can be difficult at firing at far or small targets such as an Attack Helicopter or an AC130 but is very effective against a Harrier, Pave Low, or a Chopper Gunner.

The AT4, alongside the RPG-7, does a very specific amount of damage against Harriers; the aircraft's max health (3000) minus 900.

Call of Duty: Modern Warfare 3
The AT4 was most likely used as a placeholder weapon in early builds of Call of Duty: Modern Warfare 3. It was first seen in an exclusive E3 gameplay video depicting the mission "Black Tuesday", when the player passes over an AT4 on the ground and the pick-up icon appeared. However, it is cut and replaced by the SMAW. It appears in "Persona Non Grata", where it is used by a Loyalist soldier to take down a helicopter. That soldier, ih the friendly fire is disabled via console commands, can be killed and AT4 can be picked up but not used.

Trivia

 * This is the first of the four launchers capable of both lock-on and free-fire, the others being the M72 LAW in Call of Duty: Black Ops, the SMAW in Call of Duty: Modern Warfare 3 and Call of Duty: Black Ops II, and the Stinger (in Black Ops II only).
 * When the weapon is fired in the first campaign, it will not explode when it reaches its full range, unlike the RPG-7.
 * If fired at an enemy helicopter that uses flares, the rocket will always veer away, even if free-fired, but this can be remedied by not aiming down the sights, just pressing the fire button.
 * Contrary to popular belief, the AT4 can be reused in the Modern Warfare 2 singleplayer, by pressing the weapon switch key when the player is about to toss it away. The player will retain it, which allows it to be reused by using an ammo crate with the AT4 equipped. The same quirk applies with the Stinger.
 * If the player is flashed and spins with the highest sensitivity they can clearly see the inside of the launcher, this can also be done with the Stinger.
 * On the back of the AT4, the words "Beware backblast. Hold like this." can be seen. This is most easily seen with a sniper rifle when the weapon is laying on the ground.

Video
Modern Warfare 2 - Headshot AT-4 Game Winning Kill

Video showing the accuracy of the AT4; it is accurate enough to get a headshot at medium ranges

AT4 AT4-HS AT4