I have to disagree with all the people who say athletes can't be role models. Not necessarily for what they do on the field/court/ice/etc., but for how they conduct themselves off of it. Michael Phelps is likely only a role model to swimmers, he is an amazing swimmer, if I was a swimmer I would want to swim like him.
You can't really argue with the fact that Tim Tebow would be a great role model for most young people. He spends his off season going on mission trips to third world countries, he is a leader off the field, he uses his "fame" for the benefit of others. In fact, I hate the way he plays football, but I can appreciate what he does off the field for other people.
There are many examples of athletes being role models for the stuff that they do off the field than the stuff that they do on it. Charles Barkley was right, not a role-model, an athlete. I think athletes that try to make themselves role models are the ones who probably shouldn't be, but the ones who do things for other people out of the kindness of their hearts are the role models.