Sonny dunking the bread in Clemenza's sauce: "Send somebody with him anyway." A very Italian, very "Old World" gesture.

Two deleted scenes. After Sonny breaks the news to Mama about Vito getting shot, they occur almost back to back:

Sonny, again taking a piece of bread and dipping it into a frying pan (in the novel he made himself a "sloppy sandwich of fried peppers").

Then, when Sonny walks into the Don's den, he can't bring himself to sit in Vito's chair. He clearly feels that, in some way, this would portend Vito's death. He was probably just being superstitious, but it's a VERY moving scene.