Blazing Saddles is a classic, but Three Amigos is probably one of the most underrated comedies ever. Absolutely hysterical, so many memorable scenes. To this day I still use son of a motherless goat quite often.
Lucky Day: Well, we're just gonna have to use our brains.
Ned Nederlander, Dusty Bottoms: Damn it!
Rosita: I was thinking later, you could kiss me on the veranda.
Dusty Bottoms: Lips would be fine.
Lucky Day: Oh, great. You killed the invisible swordsman!
Ned Nederlander: [runs over to check] He's dead, all right.
Dusty Bottoms: How was I supposed to know where he was?
Lucky Day: You were supposed to fire up. *We* both fired *up*.
[aside]
Lucky Day: It's like living with a six-year old.
Ned Nederlander: This is not a town of weaklings! You can use your strengths against El Guapo. Now, what is it that this town really does well?
Townspeople: Hmmm. Hmmm? Ummm.
[long pause]
Mama Sanchez: We can sew!
Dusty Bottoms: There you go, you can sew.
Ned Nederlander: Ah.
Dusty Bottoms: If only we had known this sooner.
Dusty Bottoms: Do you have anything here besides Mexican food?