Revelation 21:6

Revelation 21:6 is a framed quote in Vault 101's clinic as well as a paper note in Fallout 3.

Background
Revelation 21:6 is a passage in the New Testament of the Christian Bible. It is mentioned several times during the course of Fallout 3 by James, the Lone Wanderer's father, who says it was the favorite verse of Catherine, his deceased wife and mother of the Lone Wanderer.

The Greek letters alpha (A) and omega (Ω) are essentially the Greek counterparts of the Latin letters A and Z, meaning that God is the first and last of all things. They are also a recurring motif in Christian imagery and iconography.

As applied to the post-apocalyptic setting of Fallout, the introduction of 21:6 in the first tutorial quest can be seen as a foreshadowing of Project Purity, an attempt to purify all the irradiated water in the Tidal Basin by the Jefferson Memorial. After being reunited with James, the player learns that this passage was the inspiration for the project. In the game's climax, the code "216" is used to activate the water purifier.

It might also, depending on what path of Karma the player takes, be a prophecy of the Lone Wanderer's transformation into the new Wasteland Savior by his or her final act of self-sacrifice.

The "Better Days" holotape carries the implication that the Lone Wanderer was conceived during work on Project Purity, in the small clinic located in the Memorial's sub-basement. With the Lone Wanderer's sacrifice (if Broken Steel is not installed) to activate Project Purity, they were conceived, born and have died in the same location -- Alpha and Omega, the beginning and the end.

Location
The note is added to the Lone Wanderer's Pip-Boy when talking to their father James when first entering the Jefferson Memorial Rotunda – Project Purity – during the quest The Waters of Life.

Framed quote in Vault 101
The framed quote in James' Vault 101 office can be lockpicked during the "Trouble on the Homefront" quest (while accessible, the necessary 50 skill points are impossible to attain before escaping the vault). Among other things, it contains a Rock-It Launcher schematic, 300 caps, and an audio recording made by James around the time of the "Baby Steps" quest contemplating life in Vault 101 as a widower and new father.