Most nightmare-inducing character ?

[retrolinkx]

Well, in terms of "fuck fuck fuck not those guys" the Cazadors from New Vegas spring to mind.

But in terms of "ahhh what the fuck is that oh shit, oh shit", the SA-X from Fusion, I would hate it when I'm going somewhere and then suddenly the music stops and I hear footsteps, as well as the fact that halfway through the game, you hear that there is more than one SA-X on the ship.

Also dat intro.