Automated sentry guns have been used in countless games over the years, in a variety of different genres and settings. More often found in first person shooters and real time strategy games, sentry guns have been a staple of defensive emplacements for obvious reasons. Since they are automated, sentry guns can for the most part be left to take care of defense on their own while the player is off focusing on other matters, and any enemy foolish enough to walk into a sentry gun's line of fire will be lucky to escape in one piece. Of course, this situation is relative depending on the design of the weapon itself, it's rate of turning, it's firing arc, and other situations that could potentially make it vulnerable to attack.
Appearances in Games
In Borderlands it is the special ability of the soldier to drop down a sentry gun in battle which will automatically fire in volleys at enemies. The sentry features a shield across the front which the user can crouch behind, and can be upgraded with a variety of modifications.
Call of Duty: Black Ops
In Call of Duty: Black Ops the Sentry Gun is a killstreak reward that can be earned by getting 6 kills (5 with Hardline) without dying. The Sentry Gun is air dropped in at the spot where the player drops the canister that emits gray smoke. It costs 3,200 COD Points to unlock.
The test chambers of the Aperture Science Research Facility in the Portal games often utilise sentient automated sentries, known simply as ' Turrets'. They feature a red targeting laser, four machine guns (two on each side) and fire at any moving test subject in sight. Due to their tall bodies and thinly spread legs, they are easy to knock over and seem to have an inherent innocence about their killing.
Team Fortress 2
Perhaps the most famous ability of the Engineer class in Team Fortress 2 is to construct an automated sentry gun which locks on and fires at any targets within a large radius provided that the sentry has line of sight. It is the Engineer's primary form of attack and any kills achieved by the Sentry Gun count towards the Engineer's kills. The Sentry exists in three levels, the first of which can be built out of the Engineer's toolbox and costs 130 metal. The Sentry Gun takes a small amount of time to deploy, after which any Engineer may hit it with their wrench to repair it and spend metal in upgrading it; it costs 200 metal to upgrade it to the next available level. Due to the amount of metal it takes to build a Sentry to level 3, the highest level it can become, it is traditional for players to build a Dispenser before building a Sentry Gun.
The level 1 Sentry Gun has 150 health, 150 rounds of ammo and uses a single machine gun, the level 2 Sentry has 180 health, 200 rounds of ammo and features two gatling guns, while the level 3 Sentry has 216 health, 200 rounds of ammo for its two gatling guns and gains a rocket launcher that holds 20 salvos of 4 rockets. The Engineer may also use the Wrangler to manually control their Sentry, increase its rate of fire and generate a shield that mitigates damage inflicted on the Sentry Gun. However, switching away from the Wrangler will make the sentry shut down for a few seconds before it can function automatically again. Engineers using the Gunslinger will drop a Combat Mini-Sentry Gun instead of the regular one. Mini-Sentries cost 100 metal to build and they function like a Level 1 Sentry Gun except they construct 4 times as fast, have a 50% faster rate of fire, and each bullet deals half the damage of the standard Sentry Gun.