[HairOfTheDog]

Where was this scene beheading a hobbit? In Galadriel's mirror? or Bree? I don't remember it.

[B Knotts]

It was when the Riders had learned about "Baggins" and "Hobbiton" from Gollum shortly after Frodo had fled. They ransacked the town (and especially Bag End) searching for the Ring. Not specifically in the book, if I recall correctly.

[Paul Atreides]

After the hobbits have left Hobbiton, one of the hobbits is outside his hole listening to a horse galloping towards him; it turns out to be a Black Rider and, though it is not graphically shown, it draws its sword and there is the sound of it chopping off the hobbit's head.

[Paul Atreides]

Speaking of Galadriel's mirror, I think the most chilling scene in the movie was Frodo's glimpse of what will happen to Hobbiton should he not destroy the ring.