12 Angry Men. It lived up to the hype, which is saying a lot. The fact that a 70 year old movie could be this good even today makes it an easy 10/10.
The one thing I wish was done differently was to not show the defendant on screen. It did a very good job of using "they" to vaguely refer to people of the defendant's ilk. This allowed the term to broadly characterize an unspecified "other" and let the audience apply it metaphorically to all of our biases. Leaving the defendant unseen would have left more for the audience to wonder about. For example, at different points the audience may have questioned whether the defendant was black.