Concept art and unused models exist for cut weapons referred to as the "Kryolator" and "Kryo-Grenade." While the grenade itself made it into the Mothership Zeta DLC with a new texture and mesh, the "Kryolator" was ultimately cut in the final version of the game, existing as only a mesh with textures. However it did later appear as a usable weapon in Fallout 4.

Concept art was produced showing that there was a possible third size-class for the Super Mutants, labelled as a "Spinebreaker." In terms of size, the Super Mutant Spinebreaker would have been somewhere between the regular Super Mutant Grunts and Super Mutant Behemoths, effectively being the second size class of Super Mutants.

An unused set of Enclave Power Armor can be found in the game files and spawned in-game, utilizing console commands.

The stats differ and the armor set carries the file name, "Robo-Thor Armor", evidently a reference to Marvel Comic's Thor, as the armor helmet has a unique design reflective of Thor's own signature helmet.

The voice of the protagonist as a baby is actually Game Director Todd Howard's son, Jake Howard.

In Fallout 3, and New Vegas, a weapon can be found called the Fat Man, a Tactical Nuke Launcher.

When you fire it, it throws a mini nuke ahead of you at the enemy. When you reload you hear a "ding" sound to indicate it has finished reloading.

The bell heard is actually the Bethesda lunch room bell.

A small, playable text adventure called 'Reign of Grelock' can be accessed from a terminal in Hubris Comics.

"The Plunger Room of Death" is a small area unmarked on the Pip-Boy world map. It is located South of the Chryslus Building, and East of Farragut West Metro Station. The entrance is a door underneath an intact bridge. Inside are dozens of toilet plungers and bloody hand prints on the walls.

In the corner of the map, you can find a building called the Dunwich Building. This building is named after the H. P. Lovecraft story, The Dunwich Horror. The building also takes inspiration from other Lovecraft stories like the Cthulhu mythos.

Near the NN-03d SatCom array, a door can be found built into a rock; Upon opening it there is a wall with "Fuck You" written in green paint.

In Vault 87 is a Super Mutant that calls himself "Fawkes" locked in Isolation Room 05.

This is a reference to the comic-book V for Vendetta, where the main character (V) is originally a prisoner from "Room 5" at Larkhill Internment Camp. After escaping, V dons the infamous mask of Guy Fawkes, the real life British revolutionary known for the failed Gunpowder Plot in 1605.

Both V and Fawkes gain super strength and intellect after their experimentation, which is rare as most Super Mutants only gained super strength but suffered mental drawbacks (or even died), and in the case of V, most subjects did not survive the experiments.

Sneaking up behind and activating a Brahmin will cause your character to push it over.

Liberty Prime is loosely modeled after Gort, from the 1951 movie "The Day the Earth Stood Still."

The "Prime" in Liberty Prime is actually NOT an intentional reference to Optimus Prime from the Transformers, as many people suspected.

The Brahmin in all the Fallout games is in reference to "Brahmin" in Hindu culture, and the name likely plays on Hindu culture's reverence for cows.

However, this (and the fact that you and other NPCs can kill and eat the mutated cows) was viewed as disrespectful, which led to Fallout 3 being banned in India.

The "Experimental MIRV" (a unique Fatman) costs more to fire once than it costs to repair a regular Fat Man twice. At several hundred caps per nuke and firing eight nukes per shot, this is the most expensive weapon in the game, albeit the most powerful. It's also one of most inefficient, unnecessary, and impractical weapons in the game.

Fat Man was the codename for the atomic bomb that was detonated over Nagasaki, Japan by the United States on August 9, 1945. Because of its relation to the real historic event, the weapon was renamed to the Nuka Launcher in the Japanese version of Fallout 3. It is, however, still referred to as the Fat Man in dialogue.

Fallout 3 was originally being developed around the early 2000s by developer Black Isle Studios under the codename Van Buren. The game was an RPG similar to the previous installments played from a top-down view and would've used the engine from the canceled "Baldur's Gate III: The Black Hound". The game would've been set in the southwest of America and the story focused around a prisoner who escapes from prison and trys to discover why he was there in the first place and to stop a scientist named Presper from unleashing a virus to cleanse the world of non-pure blood humans. The project was canceled after Interplay had laid off the development team, however a tech demo was later leaked onto the internet.

In the Slaver Barracks of Paradise Falls, there is a Vault 77 Jumpsuit, with a Holotape right next to it. The Holotape is from a slaver who wants someone else to get rid of the jumpsuit that "a stranger with no name" left behind. The man recording the holotape is obviously scared and says the jumpsuit "freaks the boys out" so they must fear the stranger. The Vault 77 jumpsuit is the only one in the game and gives you a +5 to both unarmed and melee weapons.

All of these are referencing the Penny Arcade web comic "One Man, and a Crate of Puppets," which starred an unnamed Vault Dweller who was the only resident of Vault 77 and ended up hunting and killing Slavers with his bare hands and a Vault Boy puppet.

Through the use of cheats, it is possible to talk to Stockholm (the guard on top of the megaton entrance) who is usually inaccessible. When talked to, he will state:

Originally, President John Eden was meant to be voiced by former president Bill Clinton, but the team was unable to get him for the role.

After Spoiler: blowing up Megaton and encountering Moira after she becomes a ghoul, one of the player's dialogue options is "Honey, you got reeeal ugly!" This is a reference to Evil Dead 3: Army of Darkness, where Ash says this to Sheila.