Stun Grenade

Stun grenades were originally designed for the British Special Air Service as an incapacitant. Stun grenades are used to confuse, disorient, or distract a potential threat. A stun grenade can seriously degrade the combat effectiveness of affected personnel for up to a minute. Stun grenades and flash grenades are actually the same thing, but split in Call of Duty 4 and Modern Warfare 2 for balance purposes. A stun grenade does stun opponents, but has a shorter radius than the flash bang. However, stun grenades have the advantage of being fully effective whether or not the enemy is facing the grenade when it detonates, as long as it is within the blast radius. Also, the player's crosshairs will indicate whether or not an enemy was affected by the blast when it goes off, making it useful for locating enemies. It is possible to kill opposing, (or even friendly) players in Hardcore, if the player is standing on top of the grenade.

Tactics
The Stun grenade can be effectively used on a defended location or around a corner. It is typically used in close quarters combat to kill dazed enemies easily. Affected targets move and turn considerably slower than normal, so if a player throws a grenade immediately afterwards it is almost impossible to escape. There is an initial flash but vision is quickly returned. This grenade will effect the player throwing it, but not his teammates (unless friendly fire is turned on). The effect radius is smaller than the Flash grenade but makes all targets in the radius extremely vulnerable. Players with 3 may throw them all at the single location, allowing them to travel a moderate distance before the stun effects wear off. Some players use this weapon because it deals a small amount of damage to its target, thus indicating to the thrower whether or not a target has been stunned. Stun grenades can also be used to slow enemies at the beginning of a Search and Destroy round. Because enemies will not be able to rush or take positions as quickly, it can put them at a significant disadvantage in certain situations.

A direct impact from a Stun or Flash grenade will always kill somebody that is in Last Stand. Also, in Hardcore gamemodes like Hardcore Search and Destroy and Hardcore Team Deathmatch, a Direct Impact hit from a stun grenade is enough to one-shot anyone at full health unless they're using Juggernaut. Although it is extremely rare, stun or flash grenades explosions can kill a heavily wounded target, as it does 1 damage. If you cook a stun grenade in and go into Last Stand, it will turn into a frag grenade. Stun Grenades will not go off in mid-air if you throw them straight up like flash grenades would; rather, they will go off after they hit the ground.

In Modern Warfare 2, wearing a Blast Shield negates the slowing and blinding affect of stun grenades, giving Blast Shield wearers a significant advantage in indoors fighting.

This grenade is actually similar to a flash, frag and smoke grenade mix, as the grenade creates a small flash, does a little damage, and creates a negligible amount of smoke (although the flash grenade does so too.) the slowing effect is its own.

Trivia

 * In Modern Warfare 2, the stun grenade has double the draw speed than any other thrown weapon, besides the Throwing Knife.
 * In the Wii version of Call of Duty 4, players will still be able to aim at their normal speed (pointer), making stun grenades much less useful.
 * Sometimes, a stun grenade will get stuck in a wall or floor, spinning wildly. It will disappear after about 10 seconds. Sadly, it will not explode even if you shoot it.