The closest Hollywood has gotten to western/horror fusion is probably "From Dusk Till Dawn", starring our very own Danny Trejo. I'm pretty sure there'll be a veiled reference to it in-game somehow. Perhaps we'll encounter a "The Hills Have Eyes" type of scenario at some point, or one inspired by "The Texas Chain Saw Massacre."
I never got to play the DLC but there was one which centred around some mutated humans which made me think of The Hills have Eyes. Just saw the screens of the mutant hill-billy types
I got a few scares when a pack of dogs suddenly would ambushed me early on when your vulnerable, also in the buildings filled with super mutants, sometimes they run at you and when your sneaking around not expecting to get jumped by an enormous super mutant brute and your headphones are strapped on... it can give me a bit of a fright
Oh and those damn ghouls !