The Mist
The decision to take a different route vis-a-vis the original book was one of the most spectacular decisions taken in adaptation history.
Throughout the film, we are exposed to various creatures. Acid spitting spiders, flying monsters, tentacular beasts, and ginormous behemoths strolling on the roads. But this is not even the scary part. The much more unsettling element, as the movie title says, is the mist. A fog which extends its domain to every square inch outside the store which obfuscates everything outside. What you can’t see is far more dangerous than what you can see.
The ending is such a curveball, possibly one of the best turns I have seen in a bit. I would say this rivals the ending of Final Destination 5.