Atticus influenced just about every person that he came in contact with. He is one of those rare types of people that by simply knowing him, you want to make yourself a better person.
Atticus's biggest influence though is on his children, Jem and Scout. I don't think Atticus is the kind of father that every kid would enjoy having. Scout and Jem do have issues with his age, lack of aggression, and lack of desire to do "manly" stuff with them. Despite that though, every kid would still learn a lot from Atticus. He modeled for his children how a man should treat people. It doesn't matter who Atticus came in contact with. He treated them patiently, fairly, and with respect. That was never more true than when Bob Ewell spit in his face hoping to start a fight. Atticus didn't budge, and simply kept on walking. In that single moment, Atticus influenced Bob because the situation had been diffused, and he influenced Scout and Jem by showing them a new way to handle a confrontation. The reader knows that members of the town heard about the incident too; therefore, Atticus was able to influence them as well.