I like the line in Fangorn when Legolas says "I feel older in this forest, older than I have felt since traveling with you children." or something to that effect (I've got to find my book! >_<). Imagine Aragorn's dirty look, not to mention Gimli's!
Also, I like when in the Appendices, Aragorn calls "Tinuviel!" after Arwen and she smiles and says, "Why do you call me by that name?" I can just picture her thinking, "::indulgent sigh:: Yet another infatuated sap!"
"This was unexpected and rather difficult. There was some scattered clapping, but most of them were trying to work it out to see if it came to a compliment." <Love, love, love that line! They did Bilbo's line so well in the movie.
Bilbo: "I don't know half of you half as well as I should like, and I like less than half of you half as well as you deserve!"
Crowd: One or two people clap, most look at each other like, "Huh?"
I like some of the other mentioned already, like Aragorn scolding Merry about pipeweed, Quickbeam, and the 'wreathed in smoke' line. Betcha Legolas was downwind on that last one.
