You know, it's odd because I don't actually like surprises in real life. But in a book or story, I do like it when the end is not quite what I was expecting or when the writer is so skilled that it is a complete surprise. Then you can go back and re-read the story and see what you couldn't see before. That's the thing I love most about surprise endings. They sneak up on you and let you know you only thought you had a handle on where the plot was going.