All right, Bub, your ****in' head is coming right off.

Hawkeye's speech at the last supper-
Hawkeye: I just want to say one thing. Nobody ordered Walt to go on this mission.
He volunteered for certain death. That's what we award our highest medals
for. That's what being a soldier is all about.
Gloriously outrageous. But if you believed that the Vietnam War was a needless
waste of lives, also a sting of truth.

Father Mulcahy's reply to Hotlips question: "He was drafted." Always gets a laugh.

Does that- does that big ass of hers move around a lot, Frank or does it sort of lie there flaccid?

I saw it. A thing that was cold and dry. It was me. - La Belle Noiseuse

I'm an unabashed fan. Every line is a favorite line.
"We're the pros from Dover. We're here to operate." I used that one a bit when I was younger.
One line that I think gets overlookedand I didn't catch it fully until after several viewingsis when Radar has miked Hot Lips's tent as she and Frank are having sex, and their moanings and groanings are being broadcast all over camp. Hawkeye is performing surgery when he hears the ruckus over the loudspeaker. He looks up briefly, then says, "Sounds like Major Burns is performing a little dilation and curettage."
When I was a kid, I didn't understand what that meant. When I got older, and learned what a D&C is . . . a prime example of the kind of (please pardon me here) cutting humor that delights fans and infuriates detractors who label the film sexist and misogynistic. No woman I've met does not shudder at the thought of that procedure.
Make of that line what you will. As with so much of the film, it's a slap in the face to convention, and I think it's designed to provoke a reaction of some kind. To tell from the many negative comments I've read in this forum so far,
MAS*H
is still provoking a reaction more than 40 years on.
Good.
"Do your job and do it right/Life's a ballTV tonight" - Frank Zappa

when the cheerleaders chant "69 is divine!"

"You put me right off my fresh fried lobster."
When I get irritated, I say this line to myself.

"You put me right off my fresh fried lobster."
That one's found its way into my vocabulary, it seems.
I like the whole speech he gives Hot Lips at that point, with the "I might have invited you to my bed and you might possibly have come" business.
"My brain rebelled, and insisted on applying logic where it was not welcome."

Trapper yelling, while Frank is physically attacking Hawkeye: "Watch out for your goodies, Hawkeye! That man is a sex maniac!"

I like the "that man is a POW" and Trapper saying "so are you, you just don't know it"