With so many of us confessing to be underwhelmed by the comedy classic The Hangover, just what are your funniest movie comedy moments?
Three spring to mind for me though I’m sure I’ll recall more later.
When Katharine Hepburn’s dog runs off with Cary Grant’s priceless dinosaur fossil and buries it in Bringing Up Baby.
On a much cruder level, the Song of Sodomy number from Meet the Feebles.
Springtime for Hitler.
Look! It’s Enrico Palazzo!
(Really, the whole baseball game sequence from The Naked Gun)
But I liked The Hangover, so what do I know?
Clarke Griswold: “Roll’em up” as the Family Truckster rides through the hood.
Steve Buscemi’s drunken five minute rant in the Wedding Singer.
“Best damn guitar player in the world! Self taught - no lessons! Thank you Dad!”
Groucho tells Harpo “You can’t burn a candle at both ends.”
Harpo reached into his coat pocket and pull out a candle burning on both ends.
“Well, it got so that every piss-ant prairie punk who thought he could shoot a gun would ride into town to try out the Waco Kid. I must have killed more men than Cecil B. DeMille. It got pretty gritty. I started to hear the word “draw” in my sleep. Then one day, I was just walking down the street when I heard a voice behind me say, “Reach for it, mister!” I spun around… and there I was, face-to-face with a six-year old kid. Well, I just threw my guns down and walked away. Little bastard shot me in the ass.”
“We’re not Watusi…we’re not Spartans!”
The Thing About My Folks.
Peter Falk hustling the pool hustler. “We are but poor travelers…” 
Carol Kane as The Ghost Of Christmas Present in Scrooged.
Ed Helms’ song halfway through The Hangover was the one time I’ve heard a theatre audience applaud, so we’re not alone 
There are too many Leslie Nielsen moments to quote (and sadly, there’s another thread about him at the moment), but this Naked Gun monologue cracks me up just thinking about it because of the delivery of the last line:
Lily Tomlin’s first scene of being in Steve Martin’s body in “All of Me.” The first time I saw it, I actually wondered how the hell they got Lily into Steve’s body. It was that convincing.
The look on the Union General’s face in The General after the train crashes into the river.
“What hump?”
From Ruthless People, the “torture scene” where the kidnappers are faking torturing Midler’s character, who at this point knows her husband intended to kill her and is on the kidnappers side. They fake the torture over the phone using sizzling tofu patties. This part for example:
<enraged incoherent cursing by Midler>
“I’m sorry, honey. They made me say that.”
<more enraged incoherent cursing.>
“I’m sorry, they made me say that too.”
From the same movie there’s the scene where the mistress sends to the police chief what she thinks is a film of Danny DeVito killing his wife in order to force action against Danny DeVito. However, it was taken by her idiot assistant and is actually a scene of a man having sex with a prostitute (“I like my women to scream”); and as the camera pans back in the chief’s office you see that the man in question is the (rather horrified looking) chief. There’s a funny conversation which he interprets as blackmail naturally. Which leads to a later conversation where he starts complaining about her “persecuting” him, “how can you be so inhuman”, “everybody does it!”, and “Men get the urge!” Since she thinks he’s talking about Danny DeVito murdering his wife she’s rather shocked.
Steve Carell trying to report the news in Bruce Almighty while Jim Carey is jinxing him.
Steve Carell get chest-waxed in The 40 year Old Virgin. Gotta be the funniest ad-libbed bit in the last decade.
Fairly recently, the last scene in Burn After Reading, where the CIA boss reviews what we’ve learned from the adventure cracks me up.
Numerous moments from A Shot in the Dark – like the one where Clousseau spins the globe, or the bit with the pool cues.
The part in Arsenic and Old Lace where Cary Grant first discovers what his aunts are up to.
Donald O’Connor’s “Make 'Em Laugh” from Singin’ in the Rain.
Alex Karras punching out the horse.