"The Near Departed" is a short short story, written by legendary horror and science-fiction writer Richard Matheson. The story is three pages long, and I found it collected along with perhaps his most famous work, "I Am Legend".
The story has two characters: a "plain looking man" who visits a mortician, and mournfully requests mortuary service for his wife, imploring for the best possible treatment, no expenses paid. The mortician agrees, the man walks out, and because this is a story by Richard Matheson, one of The Twilight Zone's most frequent writers, we get a twist at the end. Six words change the entire story.
I was of course waiting for a twist, but thought it would be a different one than what finally happened. But this story brings up a good question: just how short can horror be? Horror depends on setting up suspense, on giving a sense of the eerie or the unusual, and then delivering on that promise. This story does do that, through its setting (it is a mortician's office, after all), and through the insistent dialog of the "plain looking man". But of course, at only three pages long, it can't quite build its setting and atmosphere up as much as a longer story, and the story (like many short short stories) might seem more like a gimmick than a story.