Doom 2 was released the same year that Kurt Cobain shot himself with a shotgun. Map21, "Nirvana" contained a shotgun in the starting sector.
I don't know about this. It's too vague. With that I mean that Nirvana is the soteriological goal for several indian religions. It's stated on the Doom wiki that the level is the opposite of the christianist level that there is in the game, meaning that this one is buddhist and it completes the life cycle on earth.
The shotgun is a very effective weapon in the game, specially agaisnt Imps that are the first enemies you encounter in the level.
So I can say that this is either pure coincidence or some type of homage.
http://en.wikipedia.org/wiki/Nirvana
http://doom.wikia.com/wiki/MAP21:_Nirvana_(Doom_II)
The fact that its vague prolly made them get away with it
