What's Your Favorite Book?

Today I entered a giveaway on The Pioneer Woman website.  (I'm a little bit obsessed with her blog and I check it religiously... don't judge.)  To enter we just had to leave a comment naming our favorite book.  This was really hard for me!  I love reading, although it seems like I read in spurts.  For a few months I'll voraciously devour any book I can get my hands on, and then I need a break for a few months before diving back in again. 
I've read a lot of books in my day.  From getting library books with my mom when I was young, to school reading, to now getting to read for fun again, there's nothing like getting lost in a good book.  But, what is my favorite book??  What book has changed/shaped my life and made a lasting impact on me?  It was really hard to choose just one. 
So I went back to the beginning.  Back to 4th grade and my favorite reading teacher, Mrs. Goolsby.  We were old enough to read to ourselves, but she read to us anyways.  Those were always everyone's favorite classes, too.  She did different voices for each character, and she always seemed to pick the BEST books!  I remember my favorite of all the books she read though, was Maniac Magee by Jerry Spinelli.  It was the first time I ever remember being emotionally involved in a book.  There were parts when the whole class almost cried, and then laughed, and then cried again. 
It was such a good book, that I remembered it even after I left Mrs. Goolsby's class.  One year for Christmas, I got the book for my brother and read it to him.  I wished I could do all the cool voices like my teacher had done when she read it.  But, voices or not, it was fun to pass my love of that book on to my brother.  I think that's what makes a book really powerful.  When it moves you emotionally, when you connect with it, when it drives you to want to share it with people you love, and when you remember it even though it's been years since you read it last. 
Anyways, since I feel another one of those summer-reading spurts coming on, I want to hear what everyone else's favorite books are.  I need some ideas of good books to read.  I enjoyed my trip down memory-lane thinking about great books I've read and I'd love to add to the list.  Anyone wanna share their favorite book?