4) Vito Corleone in The Godfather Part II
Robert De Niro as Vito Corleone may not be mute or silent, but he is certainly very quiet. Marlon Brando laid the groundwork for this character’s vocal presence, playing him with tremendous restraint and control, which we tend not to expect from mob boss characters typically. He comes off as forceful and authoritative, but also patient and thoughtful. Of course, this also makes him seem more calculating and a little frightening in his coldness, but it simultaneously makes him rather sympathetic.
De Niro takes this to the next level. Assisted by the fact that most of his lines are in Italian, he had to make the role physically and emotionally expressive to connect more with English-speaking audiences that would be stuck reading his words. Not that De Niro needs help with expressing himself through body language. The best example of this silence used to powerful effect is the famous staircase murder scene, with De Niro hiding around the corner, face frozen, coldly shooting and killing his victim with relative calm and unsettling silence, and of course not a word.