The one word that describes Atticus better than any other is "just." The whole goal of Atticus's life is to treat all people with justice. He does not want to treat anyone (even someone like Mrs. Dubose) in an unjust way. This is why he is so insistent on his kids understanding what it is like to be someone else. He wants them to see why others act the way they do (what their motives and feelings are) so they can truly judge how to act justly towards those people.
In terms of objects, I see his dress or attire, the 3-piece suit worn tight demonstrating the professionalism he employs with both his work and his children. A gun might represent Atticus because it is only used in extreme cases and as necessary. His watch seems to be a symbol. It is referenced as being carried by Jem and it is addressed in the trial. Maybe it is the passage of time that it will take, an entire generation, for racism to make a big step towards extinction.
In terms of words, I would describe Atticus as professional, moral, keen, a good judge of character, humble, gracious, kind, intelligent, and loving.