ACOG Scope: The ACOG Scope provides mid-range magnification for precision fire over long distances. The low magnification setting lends improved target acquisition outside of close-range combat, greatly improving performance in ranged battle. Assault Rifles tend to benefit the most, offering the greatest stability and mid-range performance.

Thermal Scope: The Thermal sight focuses directly on exposing enemy movement, highlighting assailants with a white-hot glow that contrasts sharply with the surrounding grayscale environment. While visibility of the surrounding area is somewhat reduced, movement is highly visible, even through the effects of a Smoke Grenade. Note that players using Assassin will not be highlighted.

Heartbeat Sensor: The Heartbeat Sensor collects heat data in the surrounding area, pinpointing enemy presence with each pulse of the radar. When defending an objective or sneaking into enemy territory, the additional surveillance warns of nearby assailants, giving you the advantage and reducing their ability to ambush your position. Note that the Heartbeat Sensor will not detect enemies using Assassin.

Variable Zoom Scope:  The Variable Zoom Scope offers three sight settings for more flexibility in your sniping. Zoom out for a better view of the ground, and then narrow in on specific targets for a larger hit profile. The different settings additionally open up more options for placement, as you’re not restricted to a single zoom.

Red Dot Sight: The Red Dot Sight offers improved target acquisition using a pinpoint LED displayed in an open mount. The additional precision provides a clearer view on target, resulting in better accuracy across all ranges and while on the move. Especially useful when attached to weapons with naturally obstructive iron sights.

Silencer:   With the Silencer equipped, shots no longer register your position on enemy radar. In addition, the reduction in muzzle flare and firing sound helps to maintain a lower profile through fire. In exchange for greater concealment, your weapon suffers a drop in effective range, reducing damage output at range.

Grip:  The Grip increases your weapon’s center speed, reducing the time it takes for the muzzle to settle after firing. In effect, this reduces recoil climb, letting you sustain continuous fire for a longer period of time before getting thrown off target. Pair with Kick for a noticeable improvement to overall accuracy.

Rapid Fire: Rapid Fire greatly increases your weapon’s firing speed, allowing for quicker takedowns at the cost of less controllable recoil. The recoil’s effects are lessened through hip fire, or with the addition of a Grip using the Attachments proficiency. Performs best in close quarters combat.

Holographic Sight: An optical sight designed to improve short- to mid-range target acquisition, the Holographic Sight functions almost identically to the Red Dot Sight. Your decision between the two is largely up to preference. While the Red Dot Sight offers a clearer view, the Holographic Sight sits higher on the mount, reducing the obscuring effect of flare and smoke through continuous fire.

Akimbo: Double your firepower with two weapons. Holding a weapon in each hand prevents you from using ADS, but the combined rate of fire drastically improves damage output. Fire both weapons simultaneously for rapid takedowns in close quarters, or fire off one and then the other for improved endurance at mid-range. Pair with Steady Aim for better handling.

Tactical knife: Attachment to gun to allow for quicker knifeing.  Useful on Pistols for quick knife kills and recovery.

Grenade Launcher: Attach a two round under-mounted Grenade Launcher for explosive area attacks, perfect for flushing enemies from cover and supporting aggressive assaults. The grenade must travel a minimum distance before impact in order to detonate, so it’s not recommended in tight areas. However, direct impact always results in an instant kill. Note that Scavenger does not resupply additional grenades.

Shotgun: Equip a twelve round under-mounted pump action Shotgun, delivering high damage at short range. The Shotgun can only be fired off the hip, requiring a close range direct hit in order to take out enemies in one shot. Highly recommended for mobile players that want a CQC option when moving through tight locations, without giving up their mid-range ability in open sight lines.

Hybrid Sight:  The Hybrid Sight offers increased combat flexibility with both a reflex sight and 4x magnification scope. Switch between one or the other depending on the current combat situation for maximum target acquisition. The application of two sights does somewhat reduce visibility, but the option to switch on the fly more than makes up for this hindrance.

HAMR Scope:  Similar to the Hybrid Sight, the HAMR Scope offers both a short range and mid range sight for increased flexibility according to the current combat situation. Design differs in that the sights are stacked, resulting in a slightly faster switch speed and a less restrictive side view.

About Attachments:    An attachment is an optional enhancement, modification or accessory for a weapon. In the first Call of Duty games, there was a lot less customization available to the player, meaning attachments were limited to the basics such as Sniper Scopes. In Multiplayer, attachments were introduced in Call of Duty 4: Modern Warfare, and since have been available in every game released afterwards.