My memory’s not so hot today but I remember really liking TRFTS, the first few seasons, anyway. I cheated and went to the quotes page at IMDb.
Homer Simpson: He did it cause he’s stupid. That’s the only reason anyone does anything.
I think that line’s truer than we’d like to admit.
You guys have the funny lines, but you’re missing the funny lines after the funny lines!
Rachel: Have I been living with him too long, or did that make sense?
Laverne & Shirley
Lenny has inherited the diner Lazlo’s Place from his late uncle. He and Squiggy renamed it “Dead Lazlo’s Place.” The girls have tried to run the business, but have not done well at it. Lenny and Squiggly have been bargaining with Frank DeFazio to sell the place to him.)
Lenny: Are you still gonna call it “Dead Lazlo’s Place”?
Frank: No!
Lenny: Good, I need the sign. Lazlo ain’t got no tombstone.
MASH is full of them.
Frank asks Father Mulcahy to do a temperance lecture and Father Mulcahy describes the time he had to do a sex lecture on the troop ship. The way William Christopher delivered it was hysterical:
Father Mulcahy: “Being celibate, I didn’t feel qualified. They brought in a Protestant. He had a film about two sailors. One was from Cleveland ostensibly, the other a small rural area. The city boy stayed on the ship and wrote his high-school sweetheart. A lovely young girl with a megaphone on her chest.”
Frank: “Father, this is a bit different.”
Father Mulcahy: “The country boy lived in a trailer with three other young ladies and a man with a whip.”
Frank: “Father?”
Father Mulcahy: “Broke his wristwatch and everything.”
Futurama - the “Bender’s Game” mini-movie, which satirized a variety of fantasy media.
Leela: Is that a hobbit over there?
Bender: No, that’s a hobo and a rabbit. But they’re making a hobbit.
Not so much a line, as I don’t believe a single word is spoken, but the opening scene to the Fraser Valentine day episode that has Niles preparing for a date @ Frasier’s house.
All in the Family: Archie is locked in the basement, drunk and freezing, and thinks the repairman unlocking the door for him is actually Jesus coming to take him to heaven.
Archie (seeing the repairman is black): Ah jeez. Jefferson was right.
MASH (From memory)
Margaret’s worried she’d pregnant. Radar allows his pet rabbit to be used for a pregnancy test (which is normally fatal for the rabbit, but not in this case, due to Hawkeye’s surgical skill. Margaret isn’t pregnant.)
Margaret: “Thank you Corporal, for letting us use Fluffy.”
Radar: “Oh, that’s okay Major. I know you’d do the same for her.”
The Simpsons (Also from memory)
(Homer’s been invited to Mr. Burns’ mansion, and excused himself to use the bathroom. He returns)
Mr. Burns: “Did you find the bathroom?”
Homer: Uh…yeah…
Larry Sanders:
Hank (after reading the recent surveys): “Artie, can I ask you a serious question?”
Art: “Sure, Hank.”
Hank (lip trembling): “Do you think I skew to an older demographic?”
*Gen. Barker: May I make a suggestion about Major Burns?
Henry Blake: Yes, Sir.
Gen. Barker: Give him a high colonic and send him on a ten-mile hike.
Capt. McIntyre: With full pack.
Gen. Barker: Good touch. *
Sorrell Booke’s expression is what really sells his last line.
From MAS*H:
Frank: Any mindless baboon can see she isn’t here, including me.
From Cheers:
(Sam is dressed as Santa as the gang is having a Christmas in July for a family. Sam is sweating in the Santa gear and wants to leave):
Sam: OK, time for us to go
Young boy: But Santa hasn’t even roasted the chestnuts yet!
Sam (fanning himself): Oh yes he has.
mmm
Let’s turn to Modern Family
Phil (talking about his fear of clowns): I am not really sure where the fear comes from, my mother says it’s cause when I was a kid I found a dead clown in the woods. But who knows?
Claire (as Mitchell tries to stop an argument between her and DeDe):She accused me of trying to steal my old boyfriend from her.
Mitchell: Okay, fine. But make it quick.
Alex: You’re a senior. Why are you still in second year math?
Haley: Not still, again.
Gloria: You can’t go around telling people what they can and can’t do.
Jay: So you’re in favor of this?
Gloria: No, it’s a freakshow! But it’s their freakshow.
I had been thinking about that scene with regard to this thread - it was dangerously close to comedy genius. 
Frasier
(Frasier has been insistent on making a video of his father. He borrowed Bulldog’s camcorder. Niles has convinced Martin to sit and speak for the video.)
Martin: Hello. I’m Martin Crane. I was 64 years old when this video was made. But now I’m dead! [As he says this last word he bugs his eyes out.]
[He continues]
I have a million bucks from when we busted a drug dealer. It’s in my Army footlocker. The combination is: Left 16, Right 32, Le-- [here he feigns dying.]
Mary Tyler Moore
(In the episode with Walter Cronkite, Ted approaches Cronkite and Lou Grant as they are about to leave. Ted still wants to get on the Network News and tries to give Cronkite a spiel about his talents.)
Baxter: Sports scores: The North Stars 3, the Kings…Oh!
Cronkite (To Lou): I’m gonna get you for this!
Grampa Simpson: “Think of me when you’re having the best sex of your life!”
Starlet O’Hara descends the staircase in her handmade dress, complete with curtain rod
Harvey Korman as Ratt Butler: “That gown is gorgeous”
Carol Burnett as Starlet O’Hara “Thank you, I saw it in the window and I just couldn’t resist it”.
Since he and Ricky move in the same “1950s entertainment” circles, George Reeves is appearing in cape and tights like you’d expect at Little Ricky’s birthday party when he suddenly needs to rescue Lucy – who’s foolishly managed to get herself into an even zanier and more dangerous situation than usual. Ricky starts ranting about how, of all the crazy things she’s done in their fifteen years of marriage…
“Ricardo, do you mean to say that you’ve been married to her for fifteen years?”
“Yeah, fifteen years!”
“And they call ME Superman!”
Another Mary Tyler Moore:
Lou Grant (giving life advice to Ted): You know how you always are?
Ted: Yeah . . .
Lou Grant: Don’t be that way.