Sentry Gun

""Like this heavy-caliber tripod mounted little old number designed by me. Built by me. And you best hope - not pointed at you.""

- The Engineer, Team Fortress 2

A mounted gun that aims and fires itself. Commonly seen in near to distant future settings. Prone to mistaken identity problems. Used for area denial or as a more flexible form of claymore mine. Might hold off a Zerg Rush. For a while.

Almost inevitably a machine gun, and may have Bottomless Magazines. Can also fire Energy Balls, especially in shoot'em ups. A stationary version of the Attack Drone.

They take several distinct appearances. Here are the most common forms of them:


 * Gun(s) mounted on legs: A gun which is put on metallic legs, usually a tripod or tetrapod. This type of Sentry Gun is commonly semi-portable and can be unmounted more easily than the rest of the subtypes.
 * A surface-mounted gun: These are the guns that look like normal guns, but are firmly mounted on place and can be found on floors, ceilings and walls. Sometimes they can also hide inside the surface they are on.
 * Hemisphere with barrel(s): This type of turret looks like a metallic hemisphere (sometimes more of a sphere is visible, sometimes less), usually with a groove where the gun barrel is located. These tend shoot to more futuristic stuff like Energy Balls, laser beams and more.
 * Core that fires stuff: This is a very simple form and can look as simple as a square with a center which fires projectiles. These normally fire slow projectiles or laser beams.

Some real life pseudo-examples exist. While the military is reluctant to give trigger-pull authority to a computer, there are many forms of remote-operated gun platforms in development and in service today, controlled by a human operator at a distance. One such device has been used to let people hunt over the internet. It was banned about twenty minutes after anyone in authority found out.

See also Weak Turret Gun.

Anime and Manga

 * Gunslinger Girl. The Agency deploys these to defend the compound, and terrorists holding a nuclear power plant make use of one to fend off the Agency assault.

Film
"Hudson: It aint stoppin' 'em, man... it aint stoppin' 'em... Come on baby, come on!
 * The Colonial Marines use some sentry guns to hold off a charge of alien drones in the director's cut of Aliens. The guns are arranged in two sets of two along a corridor. They watch in horror as the first two guns burn up all their ammo before they run out of targets...then one of the second pair...then...

Hicks: D gun's dry...C gun's down to twenty...ten... *grabs his pulse rifle in preparation for a last stand*

Ripley: No, look. They're retreating. *C gun's remote display is showing ten rounds remaining, less than a second's worth of shooting*

Hicks: Next time they walk right up and knock..."

"Edna: (into voice-activated door control) Edna Mode.
 * The Last Starfighter. The guns protecting the Starfighter base from the Kodan meteor gun attack.
 * Under Siege. A Phalanx CIWS (Close In Weapon System) aboard the battleship U.S.S. Missouri shoots down a jet fighter.
 * You Only Live Twice. The "crater guns" that Blofeld ordered to be used against Tiger Tanaka's ninja army.
 * The Empire Strikes Back. Han activates a small sentry gun, which drops out from the lower hull of the Millenium Falcon, against the snowtroopers trying to stop them escaping Hoth.
 * The Incredibles. Edna Mode is taking Elastigirl to her secret design chamber.

(multi-barreled gun immediately drops out of the ceiling to cover a startled Elastigirl)

Edna: ...and guest."


 * The Australian Exploitation Film Turkey Shoot features several close-ups of twin CCTV-controlled MG3 machine guns swiveling in a menacing fashion over the inmates of the re-education camp. When the break-out finally happens they don't hit a damn thing.
 * Judge Dredd. In the Aspen Penal Colony, Rico's cell has several automatic guns guarding him.

Literature

 * The War Against the Chtorr. The protagonist turns up at a military base and presents his ID. Several cameras swing towards him "and other things that weren't cameras." Needless to say he stands very still until his ID is verified.
 * In Twilight Watch, Anton is attacked by a Chinese-made mounted sentry gun. Since the sentry gun has no soul or is not attacking with ill intent, Anton is unable to detect or counter the gun with magical means, almost resulting in his death.
 * This novel, more than any other, shows that human technology has reached to a point where it's a serious threat to the Others, especially if it's magically-enhanced. The book's Big Bad's plan of dealing with the most powerful Other since the Middle Ages is not some complicated spell or magical artifact. A suitcase nuke will do.

Live Action TV

 * Battlestar Galactica (1970's version). The guns that protected battlestars from enemy attack.
 * Cleopatra 2525 had some BFGs that came out from the walls to defend the underground city if/when Baileys came in. But they hadn't been used in so long that nobody knew about them until they automatically deployed.
 * Eureka: In the episode H.O.U.S.E. Rules we learn that S.A.R.A.H. has been outfitted with ion cannon sentry guns.
 * One episode of MacGyver had a house defended by these.

Tabletop RPG

 * Shadowrun had several of these.
 * The Neo-Anarchists' Guide to Real Life supplement had gun ports, which were weapons mounted in walls that hosed down with a room when activated.
 * Ares Arms Sentry weapons had a modular design which allowed the addition of optional sensor packages and various weapons (e.g. machine guns and miniguns).
 * Early Champions products had a couple.
 * The Turner Snapdown Blaster system had an autofire blaster pop out of the ceiling and attack intruders.
 * The Blood and Dr. McQuark. Several automatic weapon systems were used in Dr. McQuark's base.
 * Car Wars. Autoduel Quarterly Volume 1 #4 adventure "Maniac". The Elm Grove Mall had Anti Vehicular Security Stations that fired at any vehicles moving at high speed.
 * Mutant Future has the Robo-Turret, which defended government installations before the end of civilization. It combined some kind of firearm with either a grenade launcher or a missile launcher.

Video Games

 * Almost every shooter and shoot 'em up, first or third person. To Wit:
 * Team Fortress 2 has them as the primary kill-earner of the Engineer.
 * Parts of this trope are averted with the laser designator - it does burn ammo. In standard Team Fortress 2 logic, wrench it and your metal will rearm it.
 * Starts out as a single gun. Upgrades to double chainguns and then a further upgrade gives it rockets.
 * Halo does this. At first, only you enemies have them as "Shade" turrets. In Halo 2, there are human turrets as well as the Shade turrets, which are no longer floaty. Grunts also occasionally have these that they deploy. As of Halo 3, you can rip these off their mounts can carry them as weapons.
 * Portal has cutsey ones that follow the iPod aesthetic and say adorable things as they ventilate the player.
 * Half-Life 2 has the tripod guns that can be moved or knocked over with the Gravity Gun.
 * Tribes 2 had players on defense farm them in massive numbers.
 * System Shock and its sequel used them, and let the player subvert them to his side by hacking.
 * Bio Shock has them, too. They're built on old rolling office chairs, and can also be hacked.
 * Perfect Dark had it as the secondary function of the Laptop Gun.
 * Borderlands has the Soldier's scorpio turret, that same turret as used by Crimson Lance engineers, and the massive coastal defense guns visible on some maps.
 * FEAR has drop-down ceiling turrets.
 * In Deus Ex, they can be hacked and turned against enemies.
 *  Killzone 3 's Multiplayer Engineer class
 * Golden Eye 1997 had ceiling-mounted turrets, as well as guns on tripods in one level.
 * Serious Sam series having cannon turrets in 1, cannon rocket and plasma turrets in 2 and minigun turrets in 3.
 * Quake 4 has the obligatory ceiling turrets, as well as air-dropped turrets and homing missile turrets outdoors.
 * The main Marathon trilogy doesn't feature these, but many game mods do.
 * RTS games usually don't count, as most stationary defenses are depicted as manned. However:
 * Rise of Legends has a turret drop ability for Carlini. The parachute mounted gun drones might count, as they don't move, but they don't last very long as a defensive measure.
 * Protoss turrets from Starcraft are robotic. Terran missile turrets are manned, according to the sequel at least. The automated floor and wall turrets are present in installation levels though.
 * According to the novel Shadows of the Xel'Naga, Missile Turrets are/can be automated equipment. Zerg Sunken and Spore Colonies, being living entities, sort of qualify.
 * In Starcraft II, the bunker can be upgraded to have a machine gun nest on top, with threat-recognition programming derived from Zerg instincts. There is also a pop-up flamethrower turret.
 * The Turret and Rocket Turret in Dune II.
 * Brink has The Engineer's pocket turret, which improves in power and durability with experience levels, going from a dinky little pea shooter to a 5mm-spewing monster.
 * Odd example from Beyond Good and Evil. The laser turret was a one-shot kill, but it wouldn't fire on Jade unless she was spotted by a searchlight or a guard. She could sneak right by it unscathed otherwise. It basically made some sections "must-pass" stealth sequences.
 * All Tower Defense games are built around this trope - you place multiple guns of different types down to prevent the enemies from reaching you.
 * Bullet Bill Blasters from Super Mario series are rather well-known.
 * Sentry Guns are not unheard of in Multiplayer Online Battle Arena games. For example, Heimerdinger's turrets in League of Legends and Engineer's Steam Turret (pre-change) in Heroes of Newerth act this way.
 * Sentry Guns some of the more common enemies in the Contra series.
 * Super Meat Boy has got rocket turrets and saw blade guns.
 * Champions Online features a sentry gun power in the Inventor set. It's a summon that calls two robots that can fight and follow the player or be switched into more powerful but stationary sentry gun forms.
 * "Core that shoots stuff" type in Oblivion, with floating crystals that shoot blasts of magic energy at you (and only you). Oh, and you can't do anything about them besides running and juking.
 * The SD Gundam G Generation series has turrets defending both the player and the enemy's bases, and destroying them lets the other faction take it over, which is an automatic victory. The quality of turrets gets upgraded as you progress through the game and unlock higher levels of technology.
 * Fallout 3 has two types of sentry guns but they both have only three settings, 1)friendly to your enemies 2)hostile to everyone 3) off. The last one is often achieved with a shotgun, but most have an override computer near them.
 * Mass Effect 3 has Combat Engineers, who can deploy turrets in the middle of battle. Said turrets are, per second of exposure, among the deadliest enemies in the game.
 * Splinter Cell has these. Since this is a Stealth Based Game, you can't destroy them. Instead, each one has a control console near them. The goal is to sneak past the guns and either disable them or turn off their friend/foe recognition software.
 * Tachyon the Fringe has space mines that are actually armed with lasers instead of powerful explosives. They go down from one shot, though.

Real Life

 * Close In Weapon Systems, abbreviated CIWS, of which there are several. Examples include but are not limited to:
 * The United States Phalanx CIWS, 20mm Gatling gun.
 * The Netherlands Goalkeeper CIWS, 30mm Gatling gun - based off of the same GAU-8 cannon from the A-10 Avenger.
 * The Italian DARDO CIWS, twin fast firing 40mm Bofors Cannon using High Explosive Shells.
 * The Intelligent Munition System is halfway between a sentry gun and a land mine.