Really hard to choose but 2 that stand out to me are The Elephant Man and Anatomy of a Murder.

The Elephant Man always really effected me, just made me feel viscerally uncomfortable, especially the parts with the night porter.

Anatomy of a Murder is a great courtroom drama, Jimmy Stewart was born to play the folksy small-town lawyer and George C. Scott is excellent as the ruthless prosecuting attorney. Plus the Duke Ellington score is great