I have many favorite lines. . .but here are some.
Sam: I made a promise, Mr Frodo. A promise. "Don't you leave him Samwise Gamgee." And I don't mean to. I don't mean to.
Elrond: Nine companions. So be it. You shall be the fellowship of the ring.
Pippin: Great! Where are we going?
Bilbo: My dear Bagginses and Boffins, Tooks and Brandybucks, Grubbs, Chubbs, Hornblowers, Bolgers, Bracegirdles and Proudfoots!
Everard Proudfoot: Proudfeet!
Gimli: Nobody tosses a dwarf.
Frodo: Go back, Sam. I'm going to Mordor alone.
Sam: Of course you are. And I'm coming with you.
Pippin: What's that?
Merry: This, my friend, is a pint.
Pippin: It comes in pints?
[In low voice]
Pippin: I'm getting one.
Aragorn: Gentlemen, we do not stop till nightfall.
Pippin: What about breakfast?
Aragorn: You've already had it.
Pippin: We've had one, yes. What about second breakfast?
Merry: I don't think he knows about second breakfast, Pip.
Pippin: What about elevenses? Luncheon? Afternoon tea? Dinner? Supper? He knows about them, doesn't he?
Merry: I wouldn't count on it.
Frodo: You're late.
Gandalf: A wizard is never late, Frodo Baggins. Nor is he early. He arrives precisely when he means to.
Gandalf: Confound it all, Samwise Gamgee. Have you been eavesdropping?
Sam: I haven't been droppin' no eaves sir, honest. I was just cutting the grass under the window there, if you'll follow me.
Gandalf: A little late for trimming the verge, don't you think?
Sam: I heard raised voices.
Gandalf: What did you hear? Speak.
Sam: N-nothing important. That is, I heard a good deal about a ring, and a dark lord, and something about the end of the world, but nothing important. Please, Mr. Gandalf, sir, don't hurt me. Don't turn me into anything... unnatural.
Pippin: Anyways, you need people of intelligence on this sort of... mission... quest... thing.
Merry: Well, that rules you out, Pip.
Bilbo: Are all these children yours? Gracious, you have been productive.
Pippin: Are we lost?
Merry: No
Pippin: I think we are
Merry: Shh. Gandalf's thinkin'
Pippin: Merry?
Merry: What?
Pippin: I'm hungry
Gandalf: If in doubt, Meriadoc, always follow your nose.
Sam: Trust a Brandybuck and a Took.
Merry: What? That was just a detour, a shortcut.
Sam: Shortcut to what?
Pippin: Mushrooms.
Merry: I don't know why he's so upset. It's only a couple of carrots.
Pippin: And some cabbages. And then those three bags of potatoes we lifted last week, and... and... the mushrooms, the week before.
Merry: Yes, Pippin, my point is, he's clearly over-reacting. Run.
[Merry and Pippin are leading the orcs away from Frodo]
Pippin: It's working.
Merry: I know it's working. Run.
Pippin: Oh that's nice - ash on my tomatoes.
Pippin: My tomato's burst.
Gandalf: I once knew every spell in all the tongues of Elves... Men... and Orcs.
Pippin: What are you going to do, then?
Gandalf: Knock your head against these doors, Peregrin Took! And if that does not shatter them, and I am allowed a little peace from foolish questions, I will try to find the opening words.
Merry: [On Midgewater Marshes] What do they eat when they can't have hobbit?