Which Harry Potter book is your favorite?

Question:

Which Harry Potter book is your favorite?

I just want to know the opinions of the general public. And if you don't like Harry Potter, then please don't waste your time answering this question.
Also, could you explain why?
I like the fourth one because it's the one that's full of the most action and is in my opinion the whole thing holding the series together. If JK Rowling didn't make Voldemort come back, there might as well have not been a series.
So, what do you think?

Best Answer - Chosen by Asker: My personal favourite is the most recent book 6. It's the darkest and it shows that J.K.R. respects her readers. She recognizes that they have grown up and that they can handle the darker plots. The book also reveals the most so far. It's in depth and dark and it doesn't treat us like the kids we were when we started reading. Many authors continue the same tone through out their series even though their original readers have grown up. Instead she started out with a youthful light book and has grown darker and more adult as the series has gone on. As I said this shows that she respects her readers and that she knows we want depth. She doesn't patronize or coddle us in the most recent book. The darkness of it is real and raw and true to growing teens and young adults. I can't wait to see how far she takes the last book.