Billie Jean King is in for me. Only two spots left on my list, and so many candidates. I'm considering Michael Jordan very seriously now. Seems to me he ushered in a new era of corporate sponsorship, and helped turn basketball into a more international sport, on top of being awesome on the field.
Ok, lil_brown_bat, I was tired and obviously didn't see Billie Jean King's name up on the post. Good thoughts on her contributions. I know she wasn't completely instrumental in the whole Title IX process (I meant to say "one" of the reasons, but alas, once again, I was tired; good catch on that point) but like in so many areas of life, it was her high-profile presence that provided many of the pushes you talked about. As for the rest of my list, here it is: Ali - I pick him because of the way his stand against the government was one of many things that forced social change in America. Whether you think it was a good or bad thing (the social change, that is), Ali was at the forefront of the country's resistance to the war in particular and the government in general. This is on top of what he has done since then. Truly an amazing person. Jackie Robinson - His spot on this list is unquestioned I would imagine. He broke down so many racial doors with the way he dealt with the racism as the first black ballplayer in what was then America's game (football probably holds that top spot now). Wayne Gretzky - His influence on the game of hockey can be seen in California, Arizona, Texas and Florida. There is no way the league would've expanded into those markets if his foray into Los Angeles wasn't as successful as it was (from a money standpoint, not for him, but for the league itself). While expansion might ultimately prove to be too much for the NHL to deal with in the long run, it was Gretzky who made the sport popular in the hotter places in this country. Michael Jordan - I put his Airness on my list mostly for the reasons qbert72 stated in his post. Jordan took a game that was gaining momentum in the mid-80s and shot its popularity and marketability through the roof. His excellence on the court was unquestioned but his profitability off the court (for himself and for every team and player in the NBA because of the increased product and TV revenue) might have been even more unquestioned. All you have to do is look at his feasibility now several years past his playing days. He's still one of the highest paid athlete endorsers. Tiger Woods - Basically, just read what I wrote about Jordan. The same applies for Tiger but on a grander scale, because he took a game that had a niche following (in terms of TV and marketing) and made it into one of the top sports in the country in these areas. Tournament purses increased dramatically in his wake and golf became one of TV's darlings. For proof of this all you have to do is realize that most PGA tournaments weren't even televised until the weekend before he arrived on the scene. Now, every single round of every PGA tournament is on TV somewhere. And as I've said in previous posts, Tiger made golf cool for the younger players out there. It wasn't that long ago that playing golf in high school was strictly a geek activity. Now, teams have to actually cut players because the turnout is so high.
The suggestions of King, Ali and Robinson got me thinking about the intersection between influence on a sport and influence for social change, and how it's impossible to separate the two when the athlete in question is a member of a marginalized group or a holder of a minority view. In a color-blind world, Jackie Robinson would still have a successful career, but in the world that was, he never had the option of being just a ballplayer; his presence and his color were always significant. Conversely, in a gender-blind world, Billie Jean King would almost certainly not be remembered the way she is: despite her ownership of the Grand Slam in the early '70s, in many ways she wasn't a great tennis player, not one whose technique would revolutionize the sport. She was perhaps one of the most doggedly determined and courageous competitors in her chosen arena, one who saw the broader implications of what she was doing more clearly than most at the time, and who brought the same determination to off-court battles. Ali changed heavyweight boxing; he also changed what it meant to be a black athlete in America, and broke a lot of stereotypes about what it meant to resist the Vietnam War.
That's definitely true for athletes that see their potential to impact society and are willing to accept the controversy involved. Controversy, however, can change the athletes attractiveness to companies wanting an athlete for endorsement deals. As a result, some athletes these days are pretty adamant about focusing only on the sports and don't like taking positions on issues with a larger societal impact (see Michael Jordan and Tiger Woods).
Some others worthy of a mention: Pierre de Coubertin Mark Spitz Lance Armstrong Steve Redgrave Samuel Ryder Michael Johnson History doesn't record his name, but whoever produced the football in France on Christmas Eve 1914 for the unofficial Germany vs England 50-a-side match. History doesn't record the result either, but I suspect it would be fair to assume that the Germans won on penalties.