B.J. Blazkowicz

B.J. Blazkowicz is a guard in Doom RPG, possibl the name of the Marine, the player character in the game. You find the name mentioned a log addressed to B.J. BLazkowicz discussing a hidden secret room containing a shotgun for the Marine to find.

Behind the scenes
According to the Doom RPG website "you reprise the role of the Doom Marine made famous in the groundbreaking id Software titles Doom, Doom II, and Doom 3.", suggesting that they are the same character (Doom's protagonist).