Sentry bots (military serial numbers SB-XXXX) are security robots made before the Great War with the express purpose of participating in the heaviest of firefights during war. Where the Mister Gutsy is a hovering platform with modest armor plating, and the protectron was originally designed for protecting business premises, the sentry bot is a powerhouse, equipped with sturdy armor plating, powerful weapons integrated into its chassis and high mobility, thanks to mecanum wheels mounted on its three legs.
The Appalachian variant of the sentry bot is identical to the variant of sentry bot used in the Commonwealth. They appear to have a bulkier construction and are substantially more resilient than their counterparts in the Capital Wasteland and the Mojave Wasteland. The typical weapons loadout of the sentry bot remains the same as seen in previous games, with a missile launcher and minigun being the norm (except these miniguns appear to be unique 3 barrelled variants chambered for the 5.56mm round). However, alternate weaponry configurations such as dual miniguns can also be observed.
On top of their already formidable ballistic and explosive weaponry, sentry bots have powerful melee attacks and a self-destruct function with equivalent power to a mini nuke. Despite their bulky armor and appearance, they are capable of moving stunningly fast and traversing extremely rough terrain (even scaling rocky outcrops with little difficulty that Residents would struggle to jump up on). In addition; a sentry bot's entire torso is capable of rotating independently of its legs, functioning akin to a turret and allowing it to move in one direction while shooting in a different direction (potentially against targets directly behind it). Sentry bots also appear to use Mecanum wheels that allow it to strafe right and left without having to turn.
Sentry bots are some of the rarest and the most difficult robots to defeat - fast, agile, heavily armed and resilient enough to absorb a direct hit from a mini nuke. After losing both main weapons they will initialize their self-destruct sequence and charge at the player character. Even with their ranged weaponry intact, sentry bots often charge into close combat to deliver powerful blows with their arms if one ventures too close, thus deterring attackers from any use of melee weapons. Since they explode on death with the force of a mini nuke, this tactic may prove even more dangerous to their opponent than their devastating long-range firepower. However, should a sentry bot engage the player character for too long, they will eventually enter a cooldown period, blasting steam out of their back and exposing their dual fusion cores. Hitting exposed fusion cores is the best way to cause damage to them.
Should one encounter a legendary sentry bot of any kind, keep in mind that all legendary robotic enemies explode upon death. This explosion does not override the sentry bot's built-in self-destruct, which means a legendary sentry bot will explode twice. Both explosions are equivalent to a mini nuke in power and occur with a short delay of a few seconds.
A generally non-hostile sentry bot. It is white in color and only encountered within the Whitespring Resort. It will attack other hostile creatures which come into its range, but will only attack the player character if provoked.