Ernest Hemingway was famous for his economy of style, and most American high school students are required to read his short novel, "The Old Man and the Sea." I personally prefer his short stories.
I have always admired E.B. White and James Thurber for the simplicity of their writing. Although to my knowledge neither one wrote a novel, Thurber wrote fiction; "The Secret Life of Walter Mitty" is his most well-known story, I think, and he has two collections of modern re-tellings of Aesop's fables that are quite funny.
Roald Dahl is best known for his children's books, but he also wrote for adults. His short stories have delicious "twist" endings.