The Oliphants were incredible.

The army of the dead was better than I could have imagined.
Enjoyed the movie... was a little disappointed about Minas Tirith. It looked good, but it had no life to it. The book spent quite a bit of time explaining what it was like to be a citizen of Gondor. The movie treated them all like cannon fodder.
I was surprised to see Saruman simply cast aside. Compared to the book, in the first two editions, his role was elevated.
Arwen? Sorry Pete, I like Liv Tyler as much as the next guy, but this was a bit much.
Cirith Ungol? Jackson could have spent less time on the beacon lighting and made this more than an afterthought.
Shelob? Visually stunning, but absolutely no sense at all that she was sentient.
Last, I knew that Sharkey wasn't going to make it to the movie... still, that's always been one of my favorite parts of the book.