Liberty Prime

 is a forty foot tall heavily armed U.S. Army robot brought back to working order by the Capital Wasteland Brotherhood of Steel in 2277.

Background
The original purpose of Liberty Prime was to aid American troops in the liberation of Anchorage, Alaska from communist China. Through the computer terminal at the foot of Liberty Prime, it is revealed that the project was commissioned by General Constantine Chase and was a joint effort between the U.S. Army, General Atomics, and RobCo. However, problems with the power system led to delays, and ultimately Anchorage was liberated by America in a much longer and more costly battle using their other secret weapon, the more successful and reasonably-scaled T-51b Power Armor.

Roughly two centuries later, Liberty Prime is finally pressed into service by the Capital Wasteland Brotherhood of Steel after they find him in the basement of the Pentagon.

Liberty Prime requires a massive amount of power to operate, and the Brotherhood of Steel was long unable to power him properly even with the advanced tech discovered inside the Pentagon. With the aid of Madison Li, they eventually solve this problem. His large backpack holds a seemingly inexhaustible supply of nukes, similar in potency to a Mini Nuke but several times larger. He can remove and hurl these nukes at enemies like a quarterback throwing a pass. He is also equipped with twin head-mounted lasers which will kill anything in a single hit. His massive size and strength count as weapons too: he is endowed with strength befitting a forty foot tall robot, and can rip anything in his path to shreds... if he doesn't step on it first. He can sustain massive amounts of damage and short out energy barrier fields by forcefully walking into them. Finally, to inspire his allies and demoralize foes, he constantly spouts anti-communist phrases. Like most of the robots in the game, he seems unaware that any time has passed between 2077 and the present.

Quest: Take it Back
He is first seen in the lab beneath the Citadel in his inactive state. The player can gain information about Liberty Prime as well as hear some of his dialogue by using a nearby computer terminal to initiate a dialogue test.

The Brotherhood of Steel (with the cooperation of Dr. Madison Li) manages to reactivate the robot, who then proceeds to clear the way for the Lyons' Pride to the Jefferson Memorial, where he remains until the end of the game.

Quest: Death From Above
Liberty Prime joins the player in the battle against the Enclave. After the Enclave initiates an Orbital Strike, Liberty Prime will crawl from the wreckage and initiate a self-destruct sequence to prevent his capture by the "communists." His head, both feet and what appears to be a forearm are later taken back to the Citadel. Similar to Deputy Weld, his head can be activated and he will say some of his anti-communist phrases, albeit scrambled and garbled. At the conclusion of the main quest line, Scribe Rothchild states that the Brotherhood will rebuild Prime, but it might take months or even years.

Quotes

 * "FREEDOM IS THE SOVEREIGN RIGHT OF EVERY AMERICAN."
 * "EMBRACE DEMOCRACY, OR YOU WILL BE ERADICATED."
 * "ALASKA'S LIBERATION IS IMMINENT!"
 * "BETTER DEAD THAN RED!"
 * "TACTICAL ASSESSMENT: RED CHINESE VICTORY IMPOSSIBLE."
 * "HERE TO PROTECT YOU FROM CHINESE COMMUNIST...INVASION!"
 * "COMMUNIST IS THE VERY DEFINITION OF FAILURE!"
 * "CHINESE COMMUNIST DETECTED, LETHAL FORCE ENGAGED!!!!"

Appearances
appears only in Fallout 3.

Behind the scenes

 * According to an interview in 1UP Emil Pagliarulo denied any intentional relation between Liberty Prime and Optimus Prime. Pagliarulo admitted he could have made the reference subconsciously, as he sometimes is known to do.

Bugs

 * Liberty Prime often gets stuck, especially on the left side of the highway when heading to retake the Purifier located at the Jefferson Memorial and on the first large bridge you cross
 * Liberty Prime will sometimes simply not move from his starting location. This is sometimes caused by the death of one of the Paladins, and can be fixed by finding the body (typically within the entry corridor to the Citadel) and carrying it past Prime and over the footbridge.
 * Once you complete the Broken Steel add-on, you can find Liberty Prime's severed head in the Citadel, but at the same time you can find it on the ground at the Satellite Relay Station.