Red Dot Sight

A Red Dot Sight is a type of reflex sight that specifically uses a Red Dot Laser on the middle as a reticle and precise aim. It appears in Call of Duty 4: Modern Warfare, Call of Duty: Modern Warfare 2, and Call of Duty: Black Ops.

Singleplayer
In singleplayer there are two types of Red Dot. There is the scope type, present only on the G36C and the standard M4A1. There is also the reflex type, present on silenced weapons such as the M4A1 SOPMOD and the P90-SD. This variety is used in the multiplayer.

Multiplayer
In Call of Duty 4: Modern Warfare, the Red Dot Sight is available for all weapons except sniper rifles, pistols, and the MP44 assault rifle. When selected as a weapon attachment, the red dot sight replaces the weapon's iron sights. In multiplayer, the Red Dot Sight is obtained by completing the first marksman challenge (killing 25 enemy players in total with the specified weapon) of any Assault Rifle, Submachine Gun, Light Machine Gun, or Shotgun. The Red Dot Sight is popular because it allows full peripheral vision and is clearer and easier to use than iron sights. However, the Red Dot Sight does not actually increase the weapon's accuracy.

Call of Duty: Modern Warfare 2
In Call of Duty: Modern Warfare 2, the Red Dot Sight has some changes. The new model is square, smaller, less obtrusive, and allows for a better peripheral view. For the most part, it is similar to the Red Dot Sight in Call of Duty 4. Some weapons now have their own unique Red Dot Sights. The TAR-21 uses the MARS Sight and the F2000 also uses its own red dot sight. All Red Dot Sights, except for the F2000's, are disabled when an EMP is deployed. Getting 60 kills while aiming down the red dot sight unlocks the Holographic Sight for primary weapons.

F2000 Variant
Also referred to as the "F2000 Scope" or the "F2000 Red Dot Sight", the replacement for the standard RDS is different on the F2000. It is similar in appearance to the Call of Duty 4 campaign's G36C Red Dot Sight, but is thicker, and appears as a long scope. The sight is blurry, and somewhat difficult to use at range because of this, but it does reduce the high recoil of the F2000 slightly.

Call of Duty: Black Ops
The Red Dot Sight returns in Black Ops, seen mounted on the Commando in the multiplayer teaser trailer. Unlike the Red Dot seen in previous games, this one has a different design, being more flush with the weapon. Its dot seems slightly larger than the older versions. The Red Dot also seems to be customizable, such as the smiley face on the Commando.

Trivia

 * In Call of Duty 4, the red dot sight reduces the AK-47's minimum damage from 40-30 to 40-20.
 * In Call of Duty: Modern Warfare 2, there are Akimbo TMP's with Red Dot Sights on the campaign mission No Russian, however, the sights serve no purpose.
 * In Call of Duty: World at War, there appears to be some sort of advanced version of the Red Dot Sight on the Ray Gun.
 * In Call of Duty: Modern Warfare 2, the zoom of the RDS (and other optics) varies by weapon in single player, but is the same for all weapons in multiplayer.