What Are Your Favorite SF/Fantasy Story or Novel Beginnings?

I'm currently working on a creative writing book for Abrams and writing the Beginnings chapter. I've got my own ideas about some of the best story or novel openings in the history of SF/Fantasy, but I'm curious about yours---and to make sure I don't miss anything great.So: opening sentence or sentences to a story or novel that you found particularly effective? Please include the quote and also tell us why you found it effective.I'll assume you don't mind being quoted in the book if you comment.