The PDQ-88b securitron (also named the RobCo security model 2060-B) is a private security robot created and mass-produced by House Industries with the help of RobCo Industries. Privately and on a much smaller scale, another model was produced by the Big MT research company, who were primarily attempting to improve the original. They are commonly found patrolling The Strip. They can also be found around Big MT and inside the Lucky 38.
The PDQ-88b securitron is a large, monowheel robot with a titanium alloy housing, resistant to shrapnel and small arms fire, with a screen capable of displaying a wide array of images, from static images to pre-war commercials. The PDQ-88b securitron is heavily-armed. Its left arm contains a Glastinghouse, Inc.X-25 Gatling laser for medium range engagements. For close-range suppression and crowd control, the securitron mounts a 9mm submachinegun in its right arm. However, these are only secondary weapons: concealed compartments in its shoulders contain M-235 missile launchers for long range and surface-to-air engagements, and a rapid-fire G-28 grenade launching system for close range engagements. The robots also have onboard auto-repair systems to repair any damage sustained from combat. Thus armed, a securitron can handle nearly any combat situation.
The PDQ-88b securitron supports two operating systems: Mk I and Mk II. The Mk I operating system lacks drivers for the auto-repair systems and shoulder-mounted weapons, limiting the robot's arsenal to the built-in X-25 Gatling laser and the 9mm submachinegun. The Mk II operating system enables the M-235 missile launchers, the rapid-fire G-28 grenade launching system and the auto-repair system. As estimated by Mr. House and Yes Man, the combat effectiveness of each securitron unit is improved by 235% by the upgrade.
A large number of PDQ-88b securitron units were acquired by the Big MT company for reverse engineering (fueled by Doctor 0's bitter hatred of Robert House), with the aim of creating a superior model. However, these efforts were ineffective: the only functional unit created by Doctor 0 was Muggy, a miniature, cookware-obsessed robot. Other securitrons, while benefitting from increased accuracy, firepower and more efficient self-repair routines provided by Big MT firmware (Mk I through VI), are either berserk or irreparably damaged due to critical errors in Dr 0's operating systems.
A final feature of the securitron is the housed printer inside their chassis, able to receive broadcasts and print leaflets, such as obituaries, should such an occasion occur. 
These are the models created by House Industries, the original creator of the PDQ-88b securitron, with the help of RobCo Industries. After the Great War, they are almost all controlled by Mr. House, and can be upgraded via the platinum chip.
* The securitron Mk I's on The Strip have a DT of 0. The securitrons in Freeside and inside the Lucky 38 have the normal DT of 20.
* Mark 1s have grenade launchers instead of X-25s, and will use it frequently despite them supposedly not having the software drivers for them.
Through the use of the platinum chip, the Courier may upgrade the securitrons of Mr. House or Yes Man at The Fort and around The Strip to the Mark II operating system. The securitron Mk II can use all the built-in weapons: the 9mm submachine gun, the rapid-fire G-28 25mm grenade launcher, the M-235 missile launchers, and the X-25 Gatling laser system. However, outside of the Lucky 38 basement demonstration, it only ever uses the last 3. It can also use the auto-repair systems, and its armor is increased. The unit's face is that of an American soldier wearing an M1 combat helmet and smoking a cigar.
There is a new line of securitrons created in Big MT by Doctor 0 and his team to surpass the PDQ-88b securitron created by House Industries and Robert House (the latter considered by 0 to be his greatest enemy). These efforts succeeded to a degree, as a Mk VI securitron operating system was developed. However, these never reached full production, and as of 2281, all of Big MT securitrons are either irreparably damaged or have gone berserk due to lack of maintenance for over 200 years. Because of this, they lack any functional armor, as well.
The face of the berserk PDQ-88b securitron unit is a distorted face, similar to the "angry moon" featured in the film A Trip to the Moon. The berserk model has the ability to use the rocket launchers in its shoulders and the laser in its arm, but not the grenade launcher or machine gun.
Securitrons in the Mojave Wasteland are the hands, eyes and soldiers of Mr. House. Notably, they patrol the Strip and guard its north entrance. Like all robots, securitrons cannot be pick-pocketed, and attempting to do so will just trigger the securitron to say one of their lines. The Courier may upgrade the units to the Mark II operating system through the use of the platinum chip. Those of Big MT, however, are all hostile to the Courier, with the exception of Muggy.
With a Science skill of 80 or greater, the Courier can input the following code when attempting to enter the New Vegas Strip: 1C 3C R34 M. This is "L33T-speak" for ice cream. "Ice cream" is also the code word used to identify third floor access at REPCONN headquarters.
When deactivated via the Robotics Expert perk, they will still move but cannot be interacted with. This is an issue present with many of the other robots in the game.
Outside of the Ultra-Luxe, three female NCR troopers are dancing in the water fountain, two in their underwear and the other wearing sexy sleepwear. Two securitrons will be telling them to leave, while getting more and more hostile. Eventually, two male NCR MP's will arrive and disperse the women.
The securitrons in the Las Vegas Boulevard Station and in front of the water fountain will still be Mk I, regardless of any upgrades given to the other securitrons.
Two securitrons can occasionally be seen outside of New Vegas Boulevard Station, puzzled by a piece of graffiti on the wall. They fire their Gatling lasers at it in attempt to clean it off, although this is futile and nothing actually comes off.
Securitrons seem to have police sirens in the opening cinematic. In-game, they do not ever actually use their sirens.
Father Elijah incorrectly identifies Big MT as the facility where the securitrons were developed.
If there is an NCR Ranger or trooper following the Courier, the securitrons by the Strip will shoot them.
Securitrons have a small plate just beneath their monitors that reads H&H Tools Company, implying a relation to Anthony House (Robert House's half brother).
Killing the securitrons at the Strip's gate will cause all securitrons to become hostile.
The securitrons at Big MT use the same Robco terminal symbols as Dr. 8, which can only be seen with the subtitles turned on. The securitrons will also make a beeping sound when this happens rather than Dr. 8's static sound.
It appears that they have the ability to switch AI "personalities" (I.E. Victor and Yes Man) from one securitron to any other, as Victor is seen welcoming the Courier if he goes to the Strip via NCR Monorail, and then immediately switching back to a standard securitron guard robot AI.
“Working on the Securitron was a grand adventure. He was one of the main characters and part of the main narrative of the game. The player spent quite a bit of time hanging out around the Securitron. The Securitron creature had just over 80 animations and 5 weapon types. It was fun trying to figure out where he was hiding all 5 weapon types, and how to get him to equip and reload them. I had a blast working with the character artist who molded him. We worked out how to switch screens, switch weapons, and blow off his body parts. With the advice of one of the other animators we got him to vibrate a bit all the time that way it looks like some type of car engine was working somewhere beneath his exterior. I used a lot of little tricks I've collect over the years to make this implausible character look plausible. Good times. :D”— Shon Stewart
The berserk securitrons in Old World Blues have a face similar to a piece of clip art known as "Angry Moon." This piece of clip art was taken from the cover of sheet music to the song "Stingy" by J. Fred Helf and Ed. Gardenier published in 1904.
PCPlaystation 3Xbox 360 While inside The Strip, if you kill a securitron with a head shot and destroying its TV monitor, the screen will still be present but the surrounding edges around the screen shows that the screen was destroyed. [verified]
Xbox 360 The securitrons may sometimes keep swapping weapons without even attacking the enemy. [verified]
PC When passing the Science check with the securitron gatekeeper, and talking to it again saying goodbye, the securitrons might turn hostile while attempting to enter the Strip. [verified]
PCPlaystation 3Xbox 360 It is possible that opening Mr. House's Antechamber may only cause a couple of his securitrons in his penthouse to become hostile, even after destroying some of them. [verified]
Xbox 360 Its possible that none of the securitrons will become hostile when opening Mr. House's antechamber. [verified]
PCPlaystation 3Xbox 360 The securitrons at the Battle of Hoover Dam (if you fought for an independent New Vegas) will not switch from their shoulder mounted rocket launchers, often blowing themselves up within minutes of the battle. However, if you side with House, this does not happen. [verified]
Playstation 3Xbox 360 Occasionally, a securitron may be able to use its grenade launcher despite being Mark I. [verified]
↑The Courier: "Why didn't you intervene sooner when Benny ambushed me?" Robert House: "Why didn't Victor intervene sooner, you mean? Goodsprings is a bit too far away for me to reliably control a securitron agent by remote. I can send and receive packets of data, at best. Victor's combat algorithms determined the proper course of action. Benny and his thugs were more than a match for a lone securitron. When he alerted me, I instructed him to approach the site after Benny and the others had departed." (Robert House's dialogue)
↑Robert House: "Step closer to the demonstration area, if you would... I expect you're well familiar with my securitrons by now. The titanium alloy housing that protects its electronic core deflects small arms and shrapnel easily enough... Its X-25 gatling laser, produced to spec by Glastinghouse, Inc., is deadly against soft targets at medium range... And for close-range suppression or crowd control, the securitron is armed with a 9mm submachinegun. All of this, you probably already knew... What you did not know is that these are the securitrons' secondary weapons. All this time, my securitrons have had to get by running the Mark I operating system, which lacked software drivers for their primary weapons! Today, with the delivery of the Platinum Chip, all that changes. Behold, for the first time, securitrons running the Mark II OS! The M-235 Missile Launcher gives the securitron the ability to engage ground and air targets at significantly longer ranges... And a rapid-fire G-28 grenade launching system ensures the securitron is deadly in close-range engagements. The software upgrade also includes drivers for the securitrons' highly sophisticated onboard auto-repair systems. All together, the Mark II software upgrade confers a 235% increase in combat effectiveness per unit. The city of New Vegas finally has soldiers worthy of protecting it! Return to the penthouse now. We have much to discuss..." (Robert House's dialogue)
↑Chris Avellone's blog : 0 had his moments - if his greatest creation is a tiny janitor bot that can only collect dishes, that feels in-character to me. Especially considering how far he missed his original target by (figure out what makes securitrons tick and make them better - whoops!). This clearly shows that none of the Big MT securitrons were ever functioning properly
↑Robert House: "If this statement is being broadcast, I am deceased. Please approach a securitron and take one of the printed obituaries. I, Robert Edwin House, am deceased. Please approach a securitron and take one of the printed obituaries." (Robert House's dialogue)
↑While traveling through Big MT, Dr. 0 may refer to the securitrons' dysfunctional state: "We are reading increased levels of beserkity in Securitrons from the De-Construction Plant."