The first scene at the railway station in Brief Encounter, with Celia Johnson and Trevor Howard is a moving love scene with no explicit sex, played with such conviction.
The scene in One Flew Over The Cuckoo's Nest, when the Indian speaks to Jack Nicholson for the first time is a marvellously dramatic moment. The audience has been totally fooled into thinking the Indian is dumb.
My final choice is the trial of Thomas More in A Man For All Seasons, with Paul Scofield. It is a very dramatic trial and you see an innocent man being given no chance to defend himself.