Boo Radley. Boo's supreme act of self-sacrifice comes in the final chapter when he risks his life to save Jem and Scout from the attack by Bob Ewell. But for most of his life, Boo has chosen to remain hidden inside the Radley house. At first, it is to hide his shame from the outside world in order to protect his parents' reputation. Later, it is self-imposed, in part so Boo does not have to face the gawking stares and gossip that would no doubt greet him from neighbors and townspeople.
Tom Robinson. Tom Robinson's kindness prompts him to help Mayella Ewell in the past, and he can't say no to her when she requests him to come inside the Ewell house to fix a hinge on a door. Sadly for Tom, it is a trap set by Mayella, and Tom becomes falsely accused of raping her. When Tom is later killed trying to escape, Tom's death serves as a reminder to the injustices that black men and women face in the white-dominated Deep South.
Little Chuck Little. Scout's "diminutive" classmate boldly defends his teacher, Miss Caroline, when she is threatened by Burris Ewell. Little Chuck reaches for his pocketknife and reminds Burris that "I'd soon's kill you as look at you."
Atticus Finch. Atticus risks his life for his client when he stands alone at the jail to defend Tom Robinson from the lynch mob. It is only the unexpected arrival of the children that saves Tom from a hanging and Atticus from physical harm.