Fallout: Brotherhood of Steel 2 (lost build of unfinished PlayStation 2 action role-playing game; 2000s)
Fallout: Brotherhood of Steel 2 was a cooperative action role-playing game that was being developed by Interplay Entertainment for the PlayStation 2 in Christmas 2004. It was the sequel to Fallout: Brotherhood of Steel.
The game follows a war waging between the Brotherhood of Steel and a raider group known as The Cyphers in Texas. The Cyphers are polar opposites to the Brotherhood; driving to destroy technology and stop the Brotherhood's preservation efforts. The Cyphers have come into possession of a G.E.C.K (Garden of Ethan Creation Kit). Miles Reese, who discovered the device, intends to use it to destroy human life and create a new world overrun by vegetation.
The gameplay was inspired by games such as Baldur's Gate: Dark Alliance, Diablo 2, Fallout Tactics, and the two original Fallout games.
Like the original game, the player was restricted to only picking from a range of pre-created potential protagonist characters, each having a respective skill set.
In addition to a new stealth system, the game would incorporated a reputation system that would progress the story based on the player's actions throughout their playthrough.
"Stage Bosses" would've have been battled at the end of every segment of the game.
According to Game Of The Art forum user ProgrammingAce, who leaked the design document by Brian Freyermuth, he observed that the predecessor itself was merely a source of funds for the sequel, hence its poor quality. 
The game's development began before the original, allowing for the Dark Alliance engine, which had been used for the original, to be revised. Quest structure would've been designed reminiscent of the style of the original Fallout. Like many games of the franchise, the game's style drew influence from the Mad Max series and films from the 1950s.
The game was canceled when Interplay laid off the majority of their employees. The game was never publicly announced.
The design document for the game was leaked in 2009 by Game Of The Art forum user ProgrammingAce, constituting almost all of the available information, filled with in-game photographs. Excepting page 5, the the entire document is available. No gameplay footage or game builds have surfaced.
- Fallout Van Buren (partially found unfinished Fallout game; 2000s)
- Fallout Extreme (lost build of cancelled multi-platform tactical shooter; early 2000s)
- Engadget article on Fallout: Brotherhood of Steel 2.
- Unseen64 article on Fallout: Brotherhood of Steel 2.
- Nukapedia Fallout Wiki page for Fallout: Brotherhood of Steel 2.
- The full design document of Fallout: Brotherhood of Steel 2 on Nukapedia Fallout Wiki.
- Page #3 of the design document. Retrieved 9 Jul '18
- Page #21 of the design doc. Retrieved 9 Jul '18
- Page #33 of the design doc. Retrieved 9 Jul '18
- Page #14 of the design doc. Retrieved 9 Jul '18
- Archived copy of ProgrammingAce's original post. Retrieved 9 Jul '18
- The Vault Tec Inc.'s post on cancelled Fallout games. Retrieved 9 Jul '18
- Page #4 of the design doc. Retrieved 9 Jul '18