I am sitting here nodding vigorously to all of the most posts here. I would cast a second vote to the scenes noted in #1 and #6, but they are all great. I would add the scene where Dill leaves the courtroom because he has become physically ill over what is transpiring against Tom Robinson. It is another place where Harper Lee captures the innocent yet mature response of the children to the events that the adults have created. She does such a wonderful job of blending those dichotomies.
I'm always moved by the last few pages in the novel--Scout's description of the neighborhood from Boo's point of view. Here, we understand that Scout has finally learned to see things as Boo saw them, and her perspective shifts from first to third person and she reminisces about her activities, with Jem and Dill, as she assumes Boo saw them. This is the ultimate evidence that Scout finally understands Atticus's advice that "you never really understand a person until you consider things from his point of view--until you climb into his skin and walk around in it."
The most poignant scene for me is when Atticus tells Jem that Mrs. Dubose has died. Atticus tries to make Jem see that Mrs. Dubose had good qualities (courage, perseverance) even though she had so many bad attributes and was very mean to Jem and Scout. Atticus discusses true courage:
I wanted you to see what real courage is, instead of getting the idea that courage is a man with a gun in his hand. It's when you know you're licked before you begin but you begin anyway and you see it though no matter what.
Even though Jem acts out in rage, destroys the candy box, and might not fully understand Atticus's belief that most people are good when "you finally see them," he kept Mrs. Dubose's flower. A spark of an idea was planted in Jem's mind about the dual nature of people and that people are not completely evil. Such a great scene!
Those are all excellent choices. For me, though, it's the end of the trial, when Atticus is getting ready to leave the courtroom. The Reverend tells "Miss Jean Louise" to stand up, her father's passin'. I can neither read nor watch that scene without getting all choked up. It's such a fitting tribute for a man who paid them the highest compliment--treating them as if they were actually equals. Atticus is consistent in that and does so throughout the novel; however, nothing is as moving as that moment, to me.
In Chapter 29, the shy recluse, Boo Radley, is discovered still leaning against the wall. His torn shirt, his white face and hands, his hollowed cheeks, the "shallow, almost delicate indentations at his temples," his colorless eyes, his thin, feathery hair all bespeak his deprivations. Then, when Scout points to him and a small spasm shakes him, she notices the tension drain from his face and a timid smile emerges as his image is "blurred with [Scout's] sudden tears."
Most poignant, this scene bespeaks of the oppression and deprivation of poor Boo Radley, a sensitive soul who has reached for a semblance of necessary human contact by interacting with the Atticus children.
Atticus' closing argument. Hands down, one of the best scenes ever written.
It. Never. Gets. Old.