I don’t know if this occurred to anyone else out there, but one of the first things that came to my mind when I saw the Doom 3 marine, other than the fact that he looked almost nothing like the guy in the original Doom games, was that he bore a similarity to the T-1000 in Terminator 2, otherwise known as Mr. Liquid Metal, played by Robert Patrick; probably one of the most menacing villains in any movie.
It’s the eyes, and the silence; the way the player moves that makes me think this. Okay, so the marine’s face is a little fuller than the T-1000’s gaunt looking mug, but the hair is similar. It’s just that blank expression. Similar ears too.