Unmaker

The Unmaker is a weapon in Doom 64 of demonic origin, inscribed with a pentagram and made up of parts of the spine and rib bones of a demon. It fires powerful red lasers by consuming cells as ammo.

The Unmaker has its origins in the Doom Bible, and was originally intended to be in Doom itself. According to the Doom Bible, the Unmaker was intended to be a "demon-tech weapon that hurts pure demons a lot, demon-humans very little, tech demons some. Made of demon bones. (...) The Dark Claw and Unmaker feed on human souls. Killing possessed humans or hellslaves allows the weapons to feed". This idea was later used in Doom 3's Soul Cube.

Doom 64 version
The Unmaker is the only new weapon in Doom 64. It begins as the second strongest weapon behind the BFG9000, with slightly better damage but a slower firing rate than the plasma gun. It is especially rare and can only be found in a few levels, the first one being MAP29: Outpost Omega (a secret level). The first regular level where it can be found is MAP12: Altar of Pain. However, uniquely amongst Doom weaponry, the Unmaker can be upgraded by finding the three mysterious and well-protected Demon Key artifacts:
 * The first one increases the laser speed.
 * The second key adds a second laser
 * The third one makes the weapon fire three simultaneous lasers.

The fully equipped Unmaker critically increases the chance of pain-stun, dispatching the Cyberdemon and even the mighty Mother Demon with impunity. While the BFG can dole out higher damage and strike more targets at a single time, the Unmaker arguably surpasses it in utility in the late game when it is at its full strength, strong enemies come in singles or small groups, and cell ammo is at a premium.

The weapon is never officially named within the game itself, and is kept a secret by the instruction manual. When the weapon is collected, the marine exclaims, "What the !@#%* is this!"