The heaviest class of combat robot in the United Statesmilitary, the sentry bot sacrifices speed and maneuverability for sheer resilience and overwhelming firepower. The sentry bot had become a standard piece of military equipment by at least 2063, with prototypes existing further back. The assaultron is designed for melee combat, and the Mister Gutsy is a jack-of-all-trades. The sentry bot's purpose is to engage the enemy at range with a variety of weapons, including miniguns, Gatling lasers, rocket launchers, and even back-mounted cluster grenade launchers. At the same time, its thick armor and multiple redundant systems allow it to survive extended engagements. It's commonly considered to be one of the most dangerous robots ever created and RobCo Industries' finest fighting robot. Late models are also provided with the ability to self-destruct to prevent the enemy from recovering the robot. Early sentry bot models were issued serial numbers in the SB-#### format (model, then serial), with later models transitioning to the standardized alphanumeric registration in the ABC-###### format.
They are programmed with an authoritative and professional military personality, in contrast to the "gung-ho" patriotic personality of the Mister Gutsy.
Sentry bots are the highest-level robots in Fallout 3; they are extremely durable, possessing as much health as a deathclaw but with greater Damage Resistance. Also, they do not have a weak point that can be targeted for additional damage. In fact, their heads are more durable than their torsos, though targeting the head yields a greater chance of a Critical Hit. Like other robots, sentry bots are equipped with a combat inhibitor, and will frenzy if the inhibitor is disabled. Exploiting this weakness can be helpful in dispatching other enemies, since sentry bots are among the most powerful foes in the game. Although they are quite fast, they have a slow turning rate, which can be used to the player's advantage.
Sentry bots are among the toughest enemies in the game, and present a serious threat to any low level player unlucky enough to encounter one. It is not uncommon to find sentry bots roaming the Capital Wasteland in groups of two or three at higher levels. These robots are mobile fortresses; their high level of health and lethality makes them the preeminent fighting machines of the Capital wastes.
Significantly darker in appearance, bearing a matte black painting and dark red sensors when compared to the normal variant, the Enclave model hosts improved systems. They appear at Raven Rock as well as alongside certain Enclave squads found in the wasteland. In Broken Steel, they are encountered guarding sections of the Adams Air Force Base.
The most expensive option for recruitment in Operation: Anchorage is a winterized minigun variant sentry bot, costing 4 recruitment markers. In addition to the minigun variant, there is a Gatling lazer equipped winterized sentry bot that was cut from Operation: Anchorage.
Military robots from before the Great War, painted in the characteristic olive green of the U.S. Army. They can be encountered at Fort Constantine, the National Guard depot and when wandering around the Wasteland.
This unique sentry bot is encountered in Broken Steel at the end of the Presidential metro, near the metro to the Adams Air Force Base. It holds the main fuse, which is needed to repair the nearby powerbox for the metro.
While the head of a sentry bot is the smallest part of its body, it has an increased chance for a successful hit in V.A.T.S., even when at great distances with any sort of firearm, though it can be difficult to select the head on the PC version.
Using the Robotics Expert perk on a hostile sentry bot will get the player the option to talk to it or shut it down. If the talk option is selected, the bot will only say, "Do not interfere with security operations." The player can also "talk" to a sentry bot without the perk, which will lead to the same dialog.
There is a sentry bot guarding the Citadel which will disappear after the Take it Back! quest is finished. If destroyed prior to this, however, it will respawn, allowing you a limitless supply of scrap metal, missiles, and whatever else it may carry.
Upon finishing The Superhuman Gambit, the Mechanist's robots will remain in the street (if they were destroyed previously). One or both will be sentry bots at higher levels.
There are two sentry bots in the Control Room of Raven Rock guarding the entrance to the room where President Eden can be found, and will attack the two hostile Enclave soldiers, killing them. Like other sentry bots, they can be shut down, but destroying them grants the player with only 1 experience point and negative Karma. These sentry bots also have a unique piece of dialogue, saying, "The president will see you now."
As with other types of robots, pulse grenades are especially effective against a sentry bot.
Sentry bots possess an authoritative array of speech programming, mainly expressing its current programming out loud, much like the protectron. However, sentry bots have a "deeper" voice, instilling fear in all.