Character Foils in Lord of the Rings

[Nurvingiel]

Almost every character in almost every book has another who is their equal and opposite. It's not always the main hero and the main villain who are foils. Any two characters can augment each other in the story.

My question to you is, who are character foils in Lord of the Rings?

To kick it all off, I will suggest Eowyn and Arwen. They similar in some ways, but have marked differences.

Similarities:
Both great women who get married to marry excellent men at the end of the book.
They are both heroes in their own way.
They either are or were in love with Aragorn.

Differences:
Arwen is not a warrior, Eowyn is arguably one of the greatest warriors in Middle-earth.
For most of the book, Arwen and Eowyn seek entirely different lifestyles. Arwen is not an adventurer, and operates behind the scenes. Eowyn is a warrior at heart, going so far as to disguise herself and forgo other duties to be part of the 'final' battle for Middle-earth.

What do you think?
What other character foils would you suggest?