My favorite scene is the one scene that was done in GF1 between Al Pacino and Marlon Brando. Robert Towne wrote the scene and my favorite line is "I always thought that you would be the one to pull the strings.... Senator Corleone, Gov. Corleone" That line just gives me chills. I especially like that line given that the trademark Godfather book cover and title has the Marionett strings on the letters.

Probably the best directed scene in the movie is the shooting of Sollozo and McCluskey, especially the train taking off in Mike's head