If you are thinking of a nice way to treat your son for being helpful around the house or showing good behavior, hit two birds with one stone by doing something that he loves with him.
Take him to the arcade and learn how to play his favorite video game. You may be surprised at how much fun you have trying to win prizes and beating each others' scores.
Alternately, you can pull out a box of his favorite toys, and just sit and play with him for a couple of hours. This shows your son that you are interested in what he likes, too.