Sentry Bot (Fallout: New Vegas)

Sentry bots are robots found in the Mojave Wasteland, the Big MT, and The Divide.

Background
Its successor (manufactured only in limited amounts) is the bipedal Mark II sentry bot.

Specifications
Similar to their Fallout 3 counterparts, Sentry bots found in the Mojave have two arms that end with deadly weapons (a minigun or Gatling laser on the right arm, and a missile launcher on the left), and tripod legs with wheels. They also have armored heads and as such, receive less damage from head shots. They are programmed with an authoritative, professional military personality, in contrast to the "gung-ho", patriotic personality of the Mister Gutsy model.

Sentry bot
Sentry bots are armed with an arm-mounted minigun or Gatling laser on one arm, and a missile launcher on the other. They have thick armor plating, and are very fast. Although not as common as in Fallout 3, they can still be found in various parts of the Mojave Wasteland that contain robotic guardians such as the sacrificial chamber in Vault 11 (depending on your level) or the Securitron vault.

Hardened sentry bot
A hardened sentry bot is a tougher version of the military sentry bot. They are encountered along with hardened Mister Gutsies around the crashed vertibird in the Mojave Wasteland. Hardened sentry bots have nearly twice as much health as a standard sentry bot (500 hit points as opposed to 300 hit points). However (possibly due to a developer oversight) despite what the name might suggest, they are completely unarmored with a DT of 0, unlike a standard sentry bot which has an innate DT of 18, and thus can actually survive less damage than a standard model sentry bot. One result of their increased raw health is a greater resistance to pulse grenades. This conforms with the actual electrotechnical definition of the term "hardened", meaning that hardened electronics are immune to electromagnetic pulses.

NCR sentry bot
It is similar to the military sentry bot in appearance, but is differently colored. The NCR sentry bot was originally intended to be stationed in Camp McCarran, evident in its G.E.C.K. (editor) id McCarranFieldSentryBot, but was cut from the final version of Fallout: New Vegas.

Prototype sentry bot
An antique, prototype version that can be found in the museum inside REPCONN Headquarters. It has four wheels instead of the standard three, a set of arms stemming from its back and arching around over its shoulders. Where the arms would normally join the main body in current models, it includes 3 jets on each side, as used by Mister Gutsy/Handy robots.

Excerpt from the description of the antique model in REPCONN HQ's museum:

"Whoa, watch your step! You don't want to be facing this fearsome fellow if you accidentally stumble into a restricted area. Whether sporting the latest in dual miniguns, rockets, or laser cannons, the Sentrybot not only takes its job seriously, it also takes no prisoners! It's proof of RobCo's commitment to defense that these deadly guards are concealed in chambers throughout this facility, so let this be a warning: Watch where you step, or out'll come RobCo, guns blazing!

Exhibit Brought to You By Your Friends at RobCo"

Notable sentry bots

 * RY-589 Ultimo bot

Quotes

 * This is now a free-fire zone. Non-combatants are adviced to leave the area
 * Threat assestment: Suspect at large and undamaged. Recommend full area alert
 * Non-combatants are advised to stay clear of weapons discharge
 * A lawful use of deadly force is authorized 

Bugs

 * The sentry bots in Big MT may become 'stuck' half-way in the ground making them impossible to attack.
 * There are several sentry bots stuck in the ground around Little Yangtze that cannot be looted, and can be walked through as if they are not a part of the landscape at all.