This is based on opinion. Please don't list it on a work's trope example list.
Nightmare Fuel / The Frighteners
The Grim Reaper spirit. His modus operandi of carving numbers into his victims' heads. He can also "kill" other spirits.
There's also his traveling through walls, floors, and carpets.
His second scene has him coming out of a mirror with an unholy screech, reaching into a man's chest, and squeezing the life out of his heart, killing him.
The implications of a spirit missing both chances to move on. You are stuck in this plane of existence until you just fall apart. The Judge has been around for quite a while, and showed no signs he was about to give up the ghost anytime soon. And if no one around has had near-death trauma, then the only people who can hear you are other ghosts, who are equally stranded.
Since Bartlett is able to follow Frank and Patricia when they go through the tunnel, it seems that you can hitch a ride on another spirit's ascension. Which may explain why places like hospitals often seem haunted. It's like a bus station for ghosts; they're just waiting around for the next ride out of town.
The finale in which Frank and Lucy have to evade Patricia, who's armed with a shotgun as Frank constantly shifts between the present and the past hospital, bearing witness to the horrible massacre that happened many years ago, often from the perspective of the people being slaughtered.
An example from the Director's Cut that crosses over with Squick. Frank experiences a scene where Johnny and Patricia are playing around in the morgue, and start making love on an examination table, Patricia's foot dipping into a scale filled with some corpse's innards. Gross.
"I'm in the mood for vivisection!" "Me too! Me too!" (they're referring to vivisection with a pick ax!)
Imagine you're one of the Reaper's victims; you're perfectly healthy and just minding your business when, suddenly, you get a horrible pain in your chest, like someone...or something...is crushing the life right out of your heart, to paraphrase Sheriff Perry. And you have no idea what the hell is going on. And worse, unless you're a psychic like Frank, you can't see that some dark, evil thing—actually the depraved spirit of a Serial Killer—is directly causing your heart attack. Seriously, it's Paranoia Fuel at its finest.
And where was this Reaper? What if he showed up now, before Frank had his out-of-body experience? The creature seemed able to go anywhere—inside walls, even into the floor of the jail. What if it were lurking in the walls of the medical center? What if it were in the walls of the cryolab itself?