“The son of a ***** stole my watch.”
Yep, fun romp. Wikipedia calls it an “American romantic screwball comedy mystery film”
Front Page?
I only know this one because it was my dad’s favorite movie
This one shouldn’t be too hard:
“Did you dress her up like this?”
I hadn’t actually intended that as an entry for the thread. It’s just a classic closing line akin to the ones that @terentii posted.
It is from The Front Page, which was originally a stage play and has been filmed several times. The most famous of which may have been His Girl Friday, which changed the character Hildy from a man to a woman, and changed the final line. In the 1931 version, Adolphe Menjou leans on a typewriter which makes a noise which obscures the word “bitch”. It may have been the 1974 version before the line was heard properly on film.
Wikipedia mentions a revival of the play with John Lithgow as Walter Burns. I’ll be that was a good one.
Monty Python and the Holy Grail
That’s what I was going to say.
Is this one really that hard to figure out? 
On the nosey!
One more try with this one, just because I like it so much::
“Ulysses! CHEESE!!!”
And, once more for one of mine:
David Niven in The Pink Panther?
Cary Grant in To Catch a Thief?
Nope.
One of the recruits in The Lavender Hill Mob?
Sorry, no.
“I suppose you gave him tea.”
“No. Milk.”
“May I have ten thousand marbles , please?”
Peter O’Toole in How to Steal a Million?
…still no, I’m afraid.
Drat!
If it helps, he was up for the Oscar for Best Actor for the role.