Aunt Em: "Almira Gulch, just because you own half the county doesn't mean that you have the power to run the rest of us. For twenty-three years, I've been dying to tell you what I thought of you! And now... well, being a Christian woman, I can't say it!" Of course that particular scene borders onto Moment of Awesome territory.
This Troper recalls seeing the film in theathers after 70 years and the crowd still getting a huge laugh out of this line...
Dorothy: Professor Marvel, why can't we go with you and see all the crowned heads of Europe?
Professor Marvel: Do you know any?! .... Oh, you mean the things...
Dorothy: Weren't you frightened?
Wizard of Oz: Frightened? Child, you're talking to a man who's laughed in the face of death, sneered at doom, and chuckled at catastrophe... I was petrified.
When Gilda tells the Wicked Witch to "Begone! Before someone drops a house on you!" the Witch actually looks up in alarm!
"You mean she bit ya?" "No, her dog." "Ohh...she bit her dog, eh?"