I remember Ted and Mary having that conversation on the Mary Tyler Moore show.
This, though, was between Lou and Ted:
L–“You know the way you always are?”
T–“Yeeessss…?”
L–“Don’t be that way.”
This followed Lou’s explanation to the effect that he wanted to say something to Ted but was unsure just how to put it.
Growing Pains–a conversation between Mike and Boner;
Mike: So your mother says to your father …What is your father’s name?
Boner: Sylvester.
Mike: So she says “Sylvester”…Wait a minute. Your father’s name is Sylvester Stabone?
Boner: Who knew?
ETA: Yse, I did remember this line when reading the “Boner is missing” thread.
My name is Crabby Appleton I’m rotten to the core.
I’m Tom Terrrrrrrrrrific!
From Captain Kanagaroo
From BtVS
Principal Snyder: There are some things I can just smell. It’s like a sixth sense.
Giles: No, actually, that would be one of the five.
It’s the way Giles delivers the line that makes it so funny.
And later on in the same episode, Lilith says “Isn’t it enough that I do it to your mind?”
Dammit! OK, you win this round CW – but this ain’t over!
Wow, this episode showed yesterday (I think it was on WGN), and my memory is pretty good, although the kid was a budding loan shark instead of a drug dealer.
The impact of the line wasn’t as great in the show as I remembered, because Harris had another line right afterward that I think was unnecessary (but it was in character). He said (again, quoting from memory): “Because you’re just another loser unless you can go and sign for something with dignity!”
Roddy
Babylon 5
“Mind War” episode
G’Kar: [pointing to a nearby flower] What is this?
[Upon closer inspection, an insect is visible.]
Catherine: An ant.
G’Kar: “Ant”!
Catherine: So much gets shipped up from Earth on commercial transports, it’s hard to keep them out.
[As Catherine is talking, G’Kar carefully picks up the ant.]
G’Kar: I have just picked it up on the tip of my glove. If I put it down again and it asks another ant, “What was that?”, how would it explain? There are things in the universe billions of years older than either of our races. They are vast, timeless. And if they are aware of us at all, it is as little more than ants…and we have as much chance of communicating with them as an ant has with us. We know. We’ve tried. And we’ve learned we can either stay out from underfoot, or be stepped on.
Catherine: That’s it? That’s all you know?
G’Kar: Yes. They are a mystery. And I am both terrified and reassured to know that there are still wonders in the universe…that we have not yet explained everything. Whatever they are, Ms. Sakai, they walk near Sigma 957. They must walk there alone.
“A Distant Star” episode
Sheridan: I wish I had your…faith in the universe. I just don’t see it sometimes.
Delenn: Then I will tell you a great secret, Captain. Perhaps the greatest of all time. The molecules of your body are the same molecules that make up this station, and the nebula outside, that burn inside the stars themselves. We are starstuff. We are the universe made manifest, trying to figure itself out. And as we have both learned, sometimes the universe requires a change of perspective.
“In the Shadow of Z’ha’dum” episode
Kosh: If you go to Z’ha’dum, you will die.
Sheridan: Then I die. But I will not go down easily, and I will not go down alone.
“Comes the Inquisitor” episode
[after Delenn offers to sacrifice herself for Sheridan, who’s being tortured by Sebastian]
Sebastian: You can go. You’ve passed, both of you.
Delenn: Passed what?
Sebastian: How do you know the Chosen Ones? “No greater love hath a man than he lay down his life for his brother.” Not for millions…not for glory…not for fame. For one person, in the dark, where no one will ever know or see. I have been in the service of the Vorlons for centuries, looking for you. Diogenes with his lamp, looking for an honest man willing to die for all the wrong reasons. At last, my job is finished. Yours is just beginning. When the darkness comes, know this: You are the right people, in the right place, at the right time.
“Cermonies of Light and Dark” episode
Delenn: Prophecy is a poor guide to the future. You only understand it when the event’s already upon you.
Yay! More gauntlets! 
Dude, get thee to a Netflix with haste. If you haven’t seen Firefly yet you are in for a real treat.
The Firefly experience is amazing each time, but you *always *remember the first time…
This was the moment that made me fall in love with Babylon 5–a surprising new aspect of a character who had been unsympathetic up until then, and a moment of genuine cosmic wonder.
To keep this short, I’ll just post the quotes I use on a regular basis:
Futurama:
Newslady: “Those windmills will keep him cool.”
Morbo: “WINDMILLS DO NOT WORK THAT WAY”
Arrested Development:
“Her?”
“Illusions, Michael. A trick is something a whore does for money. (sees kids listening to him)…or cocaine.”
30 Rock:
“I want to go to there.”
** Police Squad**
“Coffee?”
“Yes, I know”
Do TV talk shows count? My favorite is by the late Johnny Carson. From an online obituary:
During a 1963 show, Carson demonstrated his lightning wit, during a skit in which Ed Ames, who played an Indian on the television series Daniel Boone, was teaching Carson how to throw a tomahawk, using a cardboard cutout of a sheriff as a target. Ames duly hurled his tomahawk, which embedded itself in the sheriff’s groin. The audience was already beside itself with laughter. The mirth redoubled when Carson drily ad-libbed to his guest, “I didn’t know you were Jewish.”
Actually whenever me or my wife mispeak a person’s name we always say, “Pan” which is from The Office.
Obscure X-Files line that gets a lot of play in my house:
“Mostly?!?”
You’re wearing my shirt, Gordon.
How about a couple classic “Dick Van Dyke” episodes
On the parody of “Twilight Zone” episode called “It May Look Like a Walnut”, Dick van Dyke tells the alien he looks like Danny Thomas. The alien, well-dressed and a sophisticated British accent
responds “What…is a Danny Thomas?”. The alien was played by the show’s executive producer, Danny Thomas
On the episode “That’s my Boy?” Rob Petrie (van Dyke) is worried that their new baby was somehow switched at the hospital with a baby belong to the Peters. Finally he calls Mr Peters on the phone and has him and his wife come visit their home. When the door opens, it is the actors Greg Morris and Mimi Dillard, who are Black. The audience is hysterical between laughter and applauding over this unexpected turn of events. Finally Petrie asks “Why didn’t you tell me on the phone?” and Peters responds “And miss the expression on your face?”
This was one of the funniest things I ever saw on a Dick van Dyke show.
The classic “book 'em, Dano”, sadly the opportunity to use it rarely arises.
From MASH, a soldier has the last of the tapioca pudding but he’s not eating it Frank commandeers it and chides the soldier for being wasteful. As he digs into the pudding he says “Mmm, raisins!” the soldier deadpans, “No, flies”, which if course is why he wasn’t eating it. I couldn’t eat raisins again. So I may not use the phrase but it certainly stuck with me.
Rocko’s Modern Life: Ooop, he’s got ya there rock! I use this line on a daily basis and no one has ever gotten it.
Star Wars “Heh, it doesn’t like you” I use the Dr. Evanzan voice too. This is also used on a daily basis, one person in the 10 years I have been using this line has completed it (“I don’t like you either”) and you guys will never understand the excitement I had.