LOTR and faithfulness to subject matter.
Amy Welborn has an interesting discussion about Peter Jackson and company's explicit disavowal of any effort to explore Catholic subtexts in Tolkien's work.
As an aside, I'm not convinced by these disclaimers. There's just enough additions or extra-textual elaborations in all of the films--think Gandalf's posture as he falls into the abyss of Moria, for example--to make me think they protest too much.
I'd like to take it a step further and offer this proposal: it's probably a very, very good thing that it was not adapted by devout Catholics sensitive to those very subtexts. Such a director/writer might have been too sorely tempted to elaborate on the themes, with disastrously didactic results. Earnestness is often at war with good art, as readers of explicitly religious fiction or viewers of the Left Behind films can testify. Whereas an outsider can come to the material with a fresh eye and without the presuppositions or baggage.
The truly important thing is that Jackson, Boyens and Walsh were mostly faithful to the work, and always respectful of it even where they were not.