When I was a kid I loved to watch The Twilight Zone. That show had a huge influence on how much importance I place on the endings to my stories. The best part of TTZ was the twist-ending. While Rod Serling didn’t invent the twist-ending, he sure did make it a trademark for The Twilight Zone.
It is my opinion that a short horror story or weird tale is not complete unless it has a twist-ending. This may fly in the face of many horror or weird writers but I don’t care. The twist-ending is such a strong element that a story falls flat unless the reader is left with a bang at the end. Plus it has the added benefit of leaving a far stronger lasting impression on the reader than an ending that is nothing more than the end of the narration. Hell, a great twist-ending can turn a mediocre story into a good story simply because it is the last impression the reader is left with.
But how do you define what exactly a twist-ending is? I think that a twist-ending is when the author reveals to the reader (or viewer in the case of film) the answers to the holes in the plot in such a way that it shocks the reader (viewer). There are three basic ways this is done: 1) the author reveals to the reader a key piece of the plot that answers any ambiguities that have been left unanswered, 2) the reader has been led to conclude one direction in the plot and the author reveals something that totally turns that assumption on its head, and 3) a shock is revealed that makes the plot have a far greater ramification than the reader suspected.
I place a great deal of importance on the endings to my stories in the hopes that I achieve a twist that leaves the reader going away from the story with more to think about than just the events of the story.