>>538639967
>ghosts but it's actually all in your mind and they only appear when your sanity/morale/whatever is low
>guy who was buried alive for some reason and now thinks that he's undead
>zombies but it's the voodoo kind where they're normal people being mind controlled with drugs and suggestion
>criminals dressed as undead in some Scooby Doo tier scheme
>rumoured vampire turns out to be a blood-drinking but non-supernatural cryptid
>ghouls that are actually human cannibals mutated and turned feral by a rare prion disease
>wannabe Frankenstein trying to reanimate dead tissue, it doesn't work because reversing death is impossible but he still needs to be stopped because he's kidnapping people for his experiments
There's always a rational explanation.