re: Least-Favorite Peter Jackson changes to Lord of the Rings

Fellowship was the best of the trilogy, because he changed that the least.

Yes, he omitted Tom Bombadil, but I think he had to. That would have made the show much longer, or else cheapened the scene too much.
Similarly, the Conspiracy was drastically shortened, but they had to do that in order to get things rolling.
In other words, he edited things out for time.

Starting in Two Towers, he begins seriously changing things, and it fundamentally alters the characters.

1) He flip-flops Gandalf and Theoden about Helm's Deep; in the book Theoden wants to ride out and meet Saruman's forces on the plains, in open battle. Gandalf tells him he can't win, and his people will suffer because of that.
In the movies, Gandalf tells him to ride out to battle, and Theoden says no, we will hole up in Helm's Deep.
*this changes Theoden from an aggressive, revived warrior king who honors Gandalf's wisdom, to a bit of a curmudgeon who doesn't take advice*


2) Faramir waffling in the movie about Frodo and the Ring... in the book, he senses Frodo's burden and steers the conversation away while around others. Then, in the cave, he deduces the actual quest, and the Ring, and instantly and completely recognizes the danger, and rejects the Ring without hesitation.
*Book Faramir is the contrast to Boromir, gentler and more learned, but with more wisdom and foresight. He is the TRUE Numenorean, not Boromir, who is the product of the dilution with regular men. This also lessens the Ring significantly- Faramir recognizes that even entertaining a claim to it, hopelessly dooms you (as it did Boromir).

3) Elves at Helm's Deep...
I guess the Last Alliance wasn't the last alliance afterall...

2 huge issues with Return of the King, for me.
First, Aragorn commanding the Dead into battle... that changes his character completely.
Book- Legolas remarks that Sauron was wise to fear Aragorn, upon seeing him take command of the Dead. He could see his force of will, and the power he could wield with the Ring. But Gandalf points out that Sauron has a flaw- he's incapable of understanding that Aragorn WOULD NOT use the tools of the Enemy (like the Dead), even against the Enemy- and it makes him blind to Aragorn's true purpose.
In other words, Aragorn acts like Sauron would expect him to, in the movie. In the book, he doesn't. Sauron wins when he understands what people would do, he only loses when people act out of goodness and virtue.

The other issue, is Denethor. Movie Denethor is sniveling. Book Denethor is wise and great, proud and dignified... but embittered by the impending defeat.
Book Denethor, I think, really is touched by Pippin's innocence and frivolousness. When Pippin says "I don't know any songs worthy of the halls of Gondor", I think it breaks his somber mood, and he's serious when he tells him to sing, they need to be reminded of the peoples he protects by being on the front line. That's why Gandalf was ultimately pleased with Pippin's presence there, he eased the man's pain for awhile. In the movie, it's more like tormenting Pippin for the sake of it.