In no particular order, here are some of the events I always discuss most with students:

Bob Ewell signs his name during trial: At this moment, we learn that he is left-handed. Equally important here is the fact that Tom's left arm has been so injured that he can no longer use it. Therefore, it is impossible that Tom caused Mayella's injuries, making Bob the likely suspect.

Bob threatens Atticus: After the trial, Bob Ewell is not happy with Atticus for defending Tom and bringing his family's true nature to the forefront of town knowledge. He stops Atticus on the post office corner one morning, spits in his face, and swears to "get him" if it takes the rest of his life. Atticus doesn't seem overly bothered by this and never seems to consider that Bob will choose to "get him" by going after Scout and Jem.

Scout and Jem are attacked: After the play, Bob makes good on his threat and tries to kill Atticus's children. The children have no idea who he is in the dark, and Bob would have succeeded if they had not been rescued by a mysterious stranger.

Boo turns out to be the kids' hero: Never seen outside, Boo is the mystery of their childhood. He has remained inside and hidden all their lives, but when they need a hero, Boo emerges—never to be seen again afterward.

Jem reads to Mrs. Dubose: Mrs. Dubose says some nasty things about Atticus, and Jem responds by destroying her camellia bushes. Atticus teaches Jem that he can't respond to ugliness with ugliness and forces Jem to repay her. Mrs. Dubose asks Jem to read to her nightly, and Atticus later tells Jem that Mrs. Dubose was battling the withdrawals of an addiction; she wanted to break free of its power before she died.

Atticus is the best shot in town: When a rabid dog appears in the street, Atticus is handed the gun to shoot it. His accuracy stuns his children, who believed Atticus too old and boring to be capable of doing anything interesting. He has never shared this talent with them; Atticus is humble and never seeks glory for his abilities.

Miss Maudie's house burns down: Scout and Jem stand outside in the cold one night and watch Miss Maudie's house burn. It is her attitude following that is of significance. She shows the ability to find the good in any situation and to always move forward even following a devastating loss. This is an important lesson the children will need for the trial.

The kids talk to Mr. Dolphus Raymond: During this conversation, the kids learn that Mr. Raymond isn't the town drunk he pretends to be. Scout comments that she has never met anyone met a "being who deliberately perpetrated fraud against himself" (chapter 20). Through this discussion, the children learn that not everyone wants to fight racism in the courts or confront it every day. Mr. Raymond, who lives with a black woman and has children with her, gives people a reason to hate him besides his family. He simply pretends to be the town drunk.

Atticus stands guard by Tom's cell: Atticus knows that Tom faces danger in Maycomb while he awaits trial, and one night tensions mount. Atticus decides to stand guard by Tom's cell and confronts an angry mob who come to lynch Tom. Atticus refuses to leave, and later we learn that Mr. Underwood, a racist himself, is waiting upstairs with a gun ready to defend Atticus.

Scout diffuses the angry mob: It is not the wise words of a lawyer which convinces the mob to disperse. The gentle kindness of a young girl, noting the kindness of her father in Mr. Cunningham's entailments and that she and his son share time together at school, provides the wisdom the crowd needs to see the inherent injustice in harming Scout's father. They leave because of the wisdom of an 8-year-old.