The Sentry Gun is a multiplayer killstreak reward in Call of Duty: Modern Warfare 2. After achieving a killstreak of 5 (4 with Hardline perk), a player may call in a helicopter that will airdrop a package (similar to the Care Package killstreak) containing the sentry gun. After acquiring the package, the player can place the gun in the location of his choice. It can detect enemies at a moderate distance, with its cone of fire centered on where its user positions it. The turret can be picked up and moved; the turret is disabled while held, and the player is unable to use weapons or other equipment. If not destroyed, the turret will expire after 90 seconds, appearing to short-circuit itself.

Any players with the Cold-Blooded perk will not be targeted by the turret (though they are still vulnerable to shots fired at other targets). The sentry gun can be disabled with a single melee hit or by gunfire. A flashbang or stun grenade disables the Sentry Gun for a few seconds, leaving it vulnerable to knife. It can also be avoided by moving around its flank, outside of its firing arc. A riot shield user can approach the sentry gun and knock it down with the shield bump, or let the gun destroy itself with ricochet hits. A certain number of destroyed sentry guns will remain on the map and will only vanish when more sentry guns are placed. These destroyed guns form a visual distraction, both because players will approach them cautiously as it's hard to tell if a gun is active or disabled and because they are so bulky, allowing players to hide behind them. They can, however, be fired and walked through.

In objective-based games such as Capture the Flag or Sabotage, the Sentry gun can provide invaluable support while protecting a flag or bombsite. Even on Hardcore, the gun can absorb a decent amount of gunfire before being destroyed. However, it can be destroyed by indirect fire through predator missiles or other aerial support weapons.

Sentry Guns can be beneficial for snipers for numerous reasons. First, Snipers can only have one claymore (Without Scavenger or One Man Army) to cover them while they snipe. Sentry Guns can provide cover for the sniper rather than a claymore meaning the player does not have to sacrifice a Frag grenade, Throwing Knife, etc for a claymore. Also, unlike claymores where the enemy can come in quite close, sentry guns can keep enemies pinned down at a distance and thus, not allowing the enemy to get in close enough to shoot you at an angle or throw a grenade at you.

The Sentry Gun is a killstreak in Call of Duty: Black Ops. It requires 6 Kills, unlike 5 in Call of Duty: Modern Warfare 2. It still is required to airdrop it in. The Sentry Gun crate can't be changed due to a patch using the Hardline Pro ability the same way as a care package.

The Sentry Gun is one of the three traps available on Kino der Toten. There are 2 in the level. One is in the Theater room by theTeleporter which can be activated for 1200 and stays on for longer than the Type 92. It stays on for approximately 2 minutes and has a bigger range to kill the zombies but sadly does not work against hellhounds, and the other one is in the Foyer room, by the bottom level on a table. It can be activated for 1500 points and will stay activated for approximately 90 seconds. It will engage any zombiewithin 360 degrees of it. It is based on the Type 92 heavy machine gun from Call of Duty: World at War. It can also be found in Dead Ops Arcade.