In the Harper Lee novel, To Kill a Mockingbird, Atticus Finch is an agent of change in both a subtle and not so subtle way. First, consider how he changes the lives of his children by his moral and compassionate teachings. This effect is rather like throwing a pebble in a pond. He teaches them, and because they are changed, they go out and change others. The children and their interaction with Boo Radley is one example. Jem and his interaction with Mrs. Dubose is another example. Choosing to represent Tom is another way that Atticus effects change. While the affect this has on other people is not as readily apparent, there is no doubt that through his actions and behaviors are changing those around him.
Enotes has some great resources.