I have got to answer Misery because it contains one of my all time favorite performances in James Caan. Not to mention the screenplay being written by my all time favorite screenwriter, William Goldman, the story being terrifying, and finally, Bates' contribution, which is perfect.
My answer being duly recorded, I must say, today I'd rather watch Shawshank or Green Mile. Also, if 1408 or The Mist rears an adorable head I'm watching them, too.
I've always loved Needful Things--which I saw long before reading any sK books and probably not being aware he was even involved--mostly due to the story's concept, its connection with an embarrassing fact about humanity, but also due to Ed Harris' grand performance, as well as the actor playing the little boy, I think his name is Shane Meier, who, imho, stole the show.