Oops…I just re-read the OP. Says “scenes” not “lines.” Sorry!
The scene in Dr. Strangelove where President Merkin Muffley is on the phone to Kissoff. It’s genius. There are so many more.
The scene in The Princess Bride where Inigo, Fezzik, and Wesley (still recuperating from death) are preparing to save the princess/find the six fingered man.
Several scenes in Harold and Kumar go to whitecastle. The first is when Harold is in jail, Kumar finds the big bag of weed and proceeds to have a vision of what his life will be like with the weed. Also, the conversation Harold has with his cellmate Tarik while he’s in jail. The scene where Neil Patrick Harris comes to pay for their meal in whitecastle.
The scene in O Brother, where art thou right after Pete and Delmar get saved and they meet Tommy Johnson. There is a conversation that involves the religion of Ulysses’ car mates.
Anchorman where Jack Black kicks Ron Burgundy’s dog off the bridge and then Burgundy’s wailing in the phone booth.
Bill Murray as the sado-masochist patient in Little Shop of Horrors.
The incomparable Peter Sellers in many of the PP movies: leaning on a spinning globe, working the parallel bars and falling down the staircase, “Does your dog bite?”, the whole moat scene, which had me howling. Also, his characters in “Dr. Strangelove”.
Starsky and Hutch when they go to get the shooter who messed up their car.
“That’s not a little boy, it’s a tiny little man!”
The scene in There’s Something About Mary where he’s in Mary’s house before the prom and gets his junk caught in the zipper. Perfect, perfect buildup with more and more people coming in to look at it and being horrified before the big reveal, which looks worse than anything you imagined, then everyone deciding they’ve got to just pull the zipper down to the immediate cutaway to the ambulance with the paramedic shouting “We’ve got a bleeder!”
Just a completely masterful comedic scene, timed exquisitely throughout. I was literally crying and nearly peed my pants.
The funniest scene ever in a movie is clearly the restaurant scene in Jacque Tati’s Playtime – but only if you see it on a real movie screen in its original 70mm format. In other formats, it’s easy to miss many of the jokes.
Many of my favorites (Monty Python, Marx Brothers, Fields) have already been mentioned. I’ll add some more:
The train going over the burning bridge in The General. Not so much for what happens to the train as for the reaction of the Union general afterwards.
In Miracle of Morgan’s Creek, when Officer Kockenlocker tries to get Norbert to escape, but Norbert can’t take the hints.
The sadly overlooked “suitcase packing” scene in A Night in Casablanca.
I have never met anyone oustide my family who has Clue as their favorite movie. Clue is one of the first DVDs I ever bought!
My favorite scene has to be the whole explanation of the murders, done brilliantly by Tim Curry.
“And you got a letter and you got a letter and you got a letter and you…”
Blazing Saddles
“Where the white women at?”
“These are simple people. The common clay. The salt of the earth. You know … morons.”
Airplane!
“The shit’s gonna hit the fan, now!” :: splat ::
“The (item)? What’s that?” “It’s a (description of item), but that’s not important right now.”
Monty Python & the Holy Grail
Although the scene has been mentioned, the “Help! Help! I’m being repressed!” bit is my favorite part.
“I got better.”
“It’s just a scratch!”
“What, the curtains?”
“No, it’s too perilous.”
“Run away! Run away!”
Life of Brian
The whole “Romans go home” scene.
The Inquisition dance scene in History of the World Part I
The Inquisition, here we go
The Inquisition, what a show
We know you’re wishin’ that we’d go awaaaaaaay
But the Inquisition’s here and it’s here to stay.
My favorite line (not that you asked)is when Harvey Korman as Count deMonet says to his valet “don’t get saucy with me, Bernaise”. 
I guess you had to be there. 
OH YES! My sister (you are a girl, aren’t you?) I love this movie…I’ve watched it over and over since I first saw it at age 10. I luuuuurve Timm Curry.
I like the whole explanation of the bullets. “1 +1 +* 2* + 1…”
And “Mrs. Peacock was a man??”
“Is that what we ate?”
“I can’t take any more surprises.”
Hee hee! We’ll have to watch it together sometime! I used to think Mr. Boddy (Ving Rhames, right?) was cute. Now that my tastes have matured, I much prefer Tim Curry with that fine English accent.
Sorry about the double-post, but I just thought of another one. Stuart Little was a cute movie, but there’s a great scene after he runs away. They go to look for him, and they find his little car, jacked up with the tires removed.
The mother says, “Who would do such a thing?”
And the father says, with a disapproving frown, “Tiny little vandals.”
It was the only venture into adulthood in that whole movie, and thus very funny.
LMAO, I struggeled to decided between the scene I posted and the one you posted.
If I had to pick a favorite line, that would be it.
Ricardo Montalban’s demise in Naked Gun.
I’m taking you to task on this one. I just moved it up to the top of my NetFlix queue.
What about the exchange with Oedipus?
“Heeey, Josephus!” “Hey, mrfr!”
Sorry. Lee Ving, who is a punk singer, and also was in “Streets of Fire” & one of my personal all-time favs, “Get Crazy”
I made my own DVD of that one, since it’s not available in that format.
I nominate the scene where Lee arrives, they let him out of the trunk of the car, he goes running into a bunch of trashcans, he head-butts a cement wall 9 times, then he argues about the phrasing on the contract he’s about to sign, which he does by head-butting it the trunk of the car. . .forgot at what point he kneed the guy who used to play “Arvid” on “Head of the Class” in the groin, but it’s in there too.
That always gets me laughing but most of my other favorite lines (and scenes) involve Empress Nympho. “My tits are falling off!!”
There were many scenes from the Fawlty Towers series that had me busting a gut, but especially the “Waldorf Salad” scene in “The Americans” episode.
“Sorry. We’re fresh out of Waldorfs!” What a twit!