The scenes that always make me laugh:
GF1: Woltz's tirade to Tom: "I don't care how many daigo, wop, guinea, goombah, greasballs come out of the word-work. Now get the hell outta here!"

GF1:Badda-beep,badda-boop,badda-bip,badda-beep.

GF1: You guineas really make me laugh.

GF1: I love you with ala my heart. If I don't see you soon, I'm-a-gonna die.

GF2: When Johnny Ola calls Fredo in the middle of the night for 5 minutes and then Fredo's wife asks who was on the phone. "Wrong number."

GF2: Roth: "I'd give 4 million to be able to take a piss without it hurting."