Tough, but good, question! I have always admired the classics: O. Henry, Ambrose Bierce, Mark Twain, Edgar Allan Poe, Anton Chekhov, Washington Irving, and Henry James, to name a few. But if you want specific stories, I recommend The Unparalleled Adventures of One Hans Pfaal (a rather long short story) by Poe, An Occurrence at Owl Creek Bridge by Ambrose Bierce, and The Stranger (it could be A Stranger) by Mark Twain. Good luck!