I don't think anyone's mentioned this before- one of my favorite bits of humor, and one of those little bits of buisness that seperate the good from the great-
In GF2, during the flashback to the Festa, Vito goes to see Don Fannucci ("It looks like there's $100 under my hat." etc...) When Don Fanucci gets up to leave, he does that cheek pinch/smack on Vito's face. Vito never reacts to this until Fanucci leaves the cafe, and then De Niro swipes his fingers across his face (in that very "Don Vito" manner) and then checks the tips of his fingers, as if he's loooking for a streak of blood or (more likely) checking to make sure he got all of Fannucci's slime off. The look on De Niro's face is priceless, and it gets me every time.

Sammy The Fish orange

Say it to his face, just one time!