Darwin got in first and took all the good answers, so my list is a bit lighter.
1. One book that changed your life: Lewis's The Four Loves. I read it at 17, and it had a profound influence on my thoughts about love and friendship, making me susceptible to the intellectual wiles of the freshman Darwin.
2. One book that you've read more than once: Declare by Tim Powers. An excellent mix of historical speculation, suspense, action, love across time, and the supernatural, set against the backdrop of the Cold War.
3. One book you'd want on a desert island: Well, Darwin already took The Divine Comedy (thought I came up with it independently) so I might have to grab The Complete Works of William Shakespeare. That's pretty meaty stuff for an island sojourn. Or maybe I'd have to find a copy of Bad Twin.
4. One book that made you laugh: My Home Sweet Home by Giovanni Guareschi. Family doesn't get funnier than Margharita, the Passionaria, and Alberto.
5. One book that made you cry: I read Jane Eyre when I was 13 or 14, and found myself snuffling at Jane's stirring declaration that she was not an automaton, Mr. Rochester. It's possible that something more recent has made me tear up, but nothing springs immediately to mind -- I'm not much for crying.
6. One book that you wish had been written: The Complete User's Manual to Eleanor, Julia, and Isabel. Boy, would that make my life easier!
7. One book that you wish had never been written: Emile by Jean-Jacques Rousseau. This is the book responsible for numerous heinous theories of child and human development by perpetrating the myth of the tabula rasa -- thus rejecting the notion of original sin.
8. One book you're currently reading: A Mother's Rule of Life. I'm reading it, but I'm not liking it.
9. One book you've been meaning to read: The Death of Achilles by Boris Akunin -- fourth in the series of Erast Fandorin mysteries. These are excellent reads for anyone who loves classic mysteries, and are uber-stylish to boot.
AND I'm back, having just remembered that I wanted to tag a few people: Rick and Rhonda Lugari and BarbfromCincy in the combox, and Amber and CMinor -- time permitting for all, of course.