Attachment

Attachments are addons which can literally be attached to your weapon, and were added in Modern Warfare. They range from scopes to silencers to the miscellaneous, with each one drastically changing how you play. Generally, only one attachment can be used at any time, however with the introduction of Bling in Modern Warfare 2, two may be used at any one time. Certian weapons, such as launchers and Riot Shields, cannot use attachments.

Scopes
Scopes are the most common attachment, and replace the standard Iron sight found on all weapons, which is used for ADS. They can be added to almost all weapons, with the exception of a certain few. There are a large amount of scopes to choose from in game, including:
 * Red Dot Sights: These are found in the Modern Warfare series, and are commonly found on most weapons due to the ease of unlocking them and overall versatility. As the name suggests, it is a small glass sheet surrounded by a metal frame using optics technology to display a red dot in the center, and is fairly accurate on long distance shots.
 * MARS Sights: These are a variant of the Red Dot Sight, and are currently only present on the TAR-21. It is a circle rather than a square, and allows better vision of attachments such as a Heartbeat Sensor, but at the expense of blocking some of the players peripheral vision. On Singleplayer it is referred to as the MARS Sight, but on Multiplayer is just labelled as a Red Dot Sight.
 * EOTech HWS Holographic Sights: These once again belong to the Modern Warfare Series. This attachment is simular to the Red Dot Sight, but has a slightly larger dot, and is unlocked after a certain amount of kills looking down the Red Dot Sight. The dot moves in its respective direction as the player turns, and gives a more accurate idea of where the bullet will hit. The frame however is larger than the Red Dot Sights, and blocks peripheral vision slightly more. Most players also prefer the RDS, as the smaller dot has a better long range accuracy. It is also worth noting that this is not available on any Secondary Weapons, only certain Primary Weapons
 * AQOG Sights: Belonging to the Modern Warfare series, they are the last sight to be unlocked by getting a set amount of kills. It is alot different from the above, consisting of a black crosshair with an illuminared center, and is illuminated by Tritium, the radioactive isotope of Hydrogen, and is currently only made by Trijicon. While the ACOQ is the most accurate of the standard scopes, on some rifles it can cause increased recoil, making it unadvisable to be used on guns with an already large recoil. Many players prefer the RDS, as the ACOQ zooming methods make it difficult to use in close quaters. The ACOQ however, has the advantage of adding a substantial amount of ranged power to the gun, making it useful for long range fights.
 * SUSAT Sights: These scopes are simular to an ACOQ scope, but instead of having the Crosshair and all the fancy illuminations, it simply contains a central needle to replace the crosshair, and is only found on the L86 LSW. The scope however is just treated and named as an ACOQ Sight.
 * Thermal Scopes: These scopes are unlocked after getting a set amount of kills with an ACOQ, and are more like a Sniper sight than an ACOQ sight, as the scope can be steadied, and there is no peripheral vision outside the sight. The sight is completely unique, in that instead of just showing what the player would normally see, it instead shows the heat signitures radiating of certain objects, however this can be countered with Cold Blooded. On Hardcore modes, this scope has the ability of turning one shot Assault Rifles such as the FAL into semi-automatic snipers with a high fire rate.
 * Aperture Sights: These non-existant scopes can be found in World at War, and were put in plainly to be a replacement for the Red Dot Sight. The sight is just a circular glass sheet incased in metal containing two black lines to form a crosshair. It is unlocked after getting 75 kills with a weapon.
 * Telescopic Sights: These are found in World at War aswell, and are the equivilent of the ACOQ from Call of Duty 4: Modern Warfare, with the main difference being the chevron is black, not red. It again has problems with recoil, and like its CoD4 counterpart, has no peripheral vision.

Miscellaneous
As well as just sights, there are many other attachements, the majority of which poping up in Modern Warfare 2. These attachments are more for suiting a particular play style, and can be used to greatly enhance the players needs in combat, and in Modern Warfare 2 it is suggested to use Bling unless you know how to use an iron sight effectivly. They are:
 * Suppressors appear in both WaW and Modern Warfare. By capturing and compressing escaping gases, they reduce overall noise coming from the barrel, making yourself quiter overall and also avoiding detection on the minimap when firing. This can be especially useful for stealth classes and snipers not wanting to be detected. However, using a suppressor reduces overall range damage, which draws most players away from using the attachment. Supposedly using an ACOQ or Thermal sight neglects the problem, as they both increase range.


 * Grenade Launchers appear in both Modern Warfare games, and can be mounted on all Assault Rifles. These go underneath the gun, and literally launches a grenade at your enemies. While using a grenade launcher, you cannot aim down the sight, which makes the attachment inferior to weapons such as the Thumper, which has a far superior aiming process and firing arc. The use of a grenade launcher is frowned upon by many players, saying it is noobish, hence it's nickname, the noobtube.
 * Heartbeat Sensors appear in Modern Warfare, and are one of the attachments preferred by many. The sensor detects all enemies within a 180 degree arc up to several meters away, but can only be mounted on Primary Weapons. The heartbeat sensor uses some kind of IFF system to tell the difference between friendlies and enemies, marking enemies as red dots and friendlies as green. Currently no such gun attachment exists in real life. They are unlocked after 15 kills with a supressed weapon.
 * Foregrips appear in both Modern Warfare games, and are mainly found on Light Machine Guns and Shotguns, since it considerably reduce recoil and barrel wonder. This is therefore considered a necessity by many players, and so on Modern Warfare 2 is found alot with Bling attachments, especially those guns with Iron Sights.
 * FMJ bullets are bullets with a full metal coat when fired designed for deeper penetration in light surfaces, and is found in MW2. This is a brilliant attachment for maps such as Terminal and Highrise where most cover is made of flimsy surfaces.
 * Extended Magazines are unlocked in MW2 after a set amount of kills with FMJ penetration kills, and are said to be by far the hardest attachments to get. The extended magazine increase clip size, they do not increase total ammo carried, as that would neglect the point of Scavenger Pro.
 * Masterkey Shotgun attachments appear on Assault Rifles in MW2, and are unlocked after getting 20 kills with a grenade launcher. Oddly, they have a better range than any shotgun, and carry more ammo than most. However, despite it's appealing charactaristics, at long ranges it requires several shots, it only has a clip size of 4 and has a very low fire rate. Also, it only fires 6 pellets per slug, compared to proper shotguns using 8.
 * Akimbo appears in MW2 and allows the player to dual wield two of the gun of choice, at the expence of some accuracy, and the ability to use ADS. This appears on SMGs, Handguns, Machine Pistols and the Model 1887 & Ranger shotguns. Using Bling is again emphasised for weapons such as the 1887, as FMJ can help get bullet penetration kills much more easily.
 * Tactical Knifes allow for the player to have a knife in one hand while be able to aim down the gun with the other. Using the knife doubles the speed which it takes to stab, and, combined with a silencer when using Bling, is used alot by "knife monkeys" who like to keep themselves hidden. The attachment is only available on handguns. Dispite being able to clearly see yourself using the tactical knife attachment, no animation was made showing other players using it. This however may one day be fixed in a future patch.