"Dork!"

"When you control the mail you control information."
http://www.youtube.com/watch?v=Rg_4z2adv6Q

"KAAAAAAAAAAAMEEEEEEEEEEEEE HAAAAAAAMEEEEEEEEEEEE HAAAAAAAAAAAAAAAA!"

The Bride: Where's Bill?
The Bride: Where's Bill?
Buck: Please stop hitting me...
The Bride: WHERE'S BILL?
Buck: I-I don't know who Bill is!
-Kill Bill Vol. 1

The Bride: What are you doing here?
Bill: What am I doing? A moment ago, I was playin' my flute. But this moment, I'm looking at the most beautiful bride these old eyes have ever seen.
The Bride: Why are you here?
Bill: Last look.
The Bride: Are you going to be nice?
Bill: I've never been nice my whole life, but I'll do my best... to be sweet.
-Kill Bill Vol. 2

"Cats and dogs, living together! It's mass panic!"


Wait...

"Who the ... are Nikki and Paulo?"

"Two players, two sides. One light. The other, dark." - John Locke (Terry O'Quinn, Lost, ep. 1.2 "Pilot (part 2)")
He pretty much set up the entire theme and feel for the episodes to come with that Backgammon game. Similarly:
"I've looked into the eye of this island and what I saw was beautiful." - John Locke (Terry O'Quinn, Lost, ep. 1.5 "White Rabbit")
And many more, but particularly anything with Locke and Vincent interacting.
Oh: "I lied."

YOU JUST WON A LIFE'S SUPPLY OF WIN

"...Got any milk?"

I swear I had the post composed for hours, and once I hit submit it notified me of your post just a minute earlier.

And while I'm thinking of infamous one-liners, "ENGAGE" (oh awesome)

Anyeon who quotes Ben is full of win.

John Locke: "Where did you get electricity?"
Ben Linus: "We have two giant hamsters running in a massive wheel in our secret underground lair."

"..." - Gordon Freeman.

I think he was quoting Link when he said that.

Valve takes the reference even further with Chell saying the same thing.

"Yes," Casablanca

"Guys, quiet...do you smell that?"

"Okay, why is the fallback position sniffing each other's butts?"
Buck, Cats and Dogs 2

Seriously? No mention of "Frankly my dear, I don't give a muffins and cookies"?

"Nobody suspects the spanish inqusion!"

"Are you telling me that coconuts migrate!?"

YES Monty Python has so many great quotes, from any of the movies.
"It's just a flesh wound!"

One of the most quotable writers ever (besides Monty Python) has to be Wes Anderson:
"If what I think is happening, IS happening... It better not be." - Mrs. Fox (Fantastic Mr. Fox) This has to be my pick for best ever, at least for now.
"Why'd you take your shoes off?" "So I don't break your nose when I kick it." - Beaver's son, Kristofferson (Fantastic Mr. Fox)
"I saved Latin. What did you ever do?" - Max Fischer (Rushmore)
And way, way more I remembered after watching once, which almost never happens.

I second "DON'T PANIC" though that's not exclusive to the movie.
"Share and Enjoy!" - Sirius Cybernetics Cooperation, Complaints Division (The Hitchhiker's Guide to the Galaxy) Wait that's not from the movie... I think...
"Zaphiod's just this guy, you know?"
"But this isn't a presidential release of prisoner form, those are blue!" (hmm would I call that best ever?)
"Buttons aren't toys!"

Do I have to pick just one? It's kind of hard to pick an awesome line that stands out on it's own, everything is so contextual, maybe we should start a thread for best overall scenes?

Oh wait, oh wait, I got one!

"You're tearing me APART, Lisa!"

I would quote Nick from L4D2, but his quotes include quite colorful words.

http://en.wikiquote.org/wiki/It%27s_Always_Sunny_in_Philadelphia

In particular...

Lawyer- In fact, I don't think that you know anything about law practice.

Charlie- Okay dude, if we toe to toe on bird law, I'd have you stumped.

Lawyer- Bird law does not exist.

Charlie- Says someone who knows nothing about the law!

"Don't tell me what I can't do."

McGeek, McGPS, McCoffee... There're about a billion nicknames for poor Timothy McGee in NCIS.

"A bunch of baby ducks, Send them to the moon! Soda machine that doesn't work, Send it to the moon!"

EDIT: Since Naylorfan already put one:

"And here we see Byrd, spelled with a "y" instead of an "I". Because poor literacy is Kewl!"

"...treating illnesses is why we became doctors, treating patients is what makes most doctors miserable."

"The treatments don't always work. Symptoms never lie."

"It's a basic truth of the human condition that everybody lies. The only variable is about what."

"Never trust doctors."

-Dr. House.

"It's over 9000!"

Enough has been said

"Vegeta what does the scouter say about his power level?"

"I'm gonna send this planet and everyone on it into another dimension!"

Quote Nazi. Also: hy didn't you people do that when I said kamehameha?

"I’ll Get You Next Time! Gadget! Next time!!!"- Dr.Claw

Bedevere: How do you know she is a witch?
Peasant: She looks like one.
[Crowd indistinctly shouts]
Bedevere: Bring her forward!
Girl: I'm not a witch.
Bedevere: But you are dressed as one...
Girl: They dressed me up like this. [Crowd murmurs]
Girl: And this isn't my nose. This is a false one.
Bedevere: [inspects the nose and confirms] Well?
Peasant: Well, we did do the nose.
Bedevere: The nose?
Peasant: And the hat. She's a witch!
Peasant Crowd: Burn her!
Bedevere: Did you dress her up like this?
Peasant Crowd: No, no, no! [beat] Yes, yes. A bit. But she's got a wart.
Bedevere: Why do you think that she is a witch?
Peasant: Well, she turned me into a newt.
[Bedevere gives him a disbelieving look]
Bedevere: A newt?
[Silence]
Peasant: Well, I got better.
Peasant Crowd: Burn her anyway!

Frenchman: You don't frighten us, English pig-dogs! Go and boil your bottoms, sons of a silly person! I blow my nose at you, so-called Ah-thoor Keeng, you and all your silly English K-n-n-n-n-n-n-n-niggits! [makes taunting gestures at them]
Sir Galahad: What a strange person.
King Arthur: Now, look here, my good man--
Frenchman: I don't want to talk to you no more, you empty-headed animal food trough water! I fart in your general direction! Your mother was a hamster and your father smelt of elderberries! Now leave before I am forced to taunt you a second time!

Sir Lancelot: Look, my liege! [trumpets blare to a shot of a castle]
King Arthur: [awed] Camelot!
Sir Galahad: Camelot!
Sir Lancelot: Camelot!
Patsy: It's only a model.
King Arthur: Shh! Knights, I bid you welcome to your new home. Let us ride to Camelot!
[The inhabitants of Camelot sing "Knights of the Round Table"]
Knights of the Round Table: [singing and dancing] We're knights of the Round Table, we dance whene'er we're able. We do routines and chorus scenes with footwork impec-cable, We dine well here in Camelot, we eat ham and jam and Spam a lot. / We're knights of the Round Table, our shows are for-mi-dable. But many times we're given rhymes that are quite un-sing-able, We're opera mad in Camelot, we sing from the diaphragm a lot. / In war we're tough and able, Quite in-de-fa-ti-gable. Between our quests we sequin vests and impersonate Clark Gable / It's a busy life in Camelot.
Knight: I have to push the pram a lot.
[Cut back to Arthur]
King Arthur: On second thoughts, let's not go there. It is a silly place.

Monty Python and the Holy Grail is possibly the best movie ever.

"We finally have proof that aliens walk among us." -Raj, The Big Bang Theory (Season 3 Finale)

"It's always Christmas in Heaven." -The Meaning of Life
*pukes* -Super Size Me
"Oh my God, there's **** EVERYWHERE!" -Dumb and Dumberer
"All dogs go to heaven because, unlike people, dogs are naturally good and loyal and kind." -Annabelle All Dogs Go to Heaven

You are awesome.

"You wanna intimidate someone, give 'em the LAAAAZZZY EYE."

"Let Your Freak Flag Fly!"
-Celia.

"Caaarl!"
- Paul, Llamas with hats.

"Say Hello to my Little Friend! >:(!!!"
-Tony M., Scarface.

"Imagination..."
-Sponge Bob