Unusually for a Mathematical Ninja, Billy Beane isn't a mathematician. Nor is he dead. He's a baseball manager.
Now, I don't know one end of a baseball stick from another, so this will be strewn with errors: one thing I do know, thought, is that if I was a baseball fielder, those errors would be tracked and analysed to the nth degree.
You see, Billy Beane was one of the first baseball managers to apply maths to the sport when he became General Manager of the Oakland Athletics in 1997. Not just in a "this player has a better average than this player" sort of way - scouts and journalists have done that forever - but in a 'what behaviours win baseball matches?' sort of way. Beane didn't do the sums himself - he hired smart people to do that for him - but he was the first to implement a completely new baseball strategy based on 'sabermetrics' - a detailed analysis of how the game works. (Sabermetrics is named after the Society for American Baseball Research).
Traditionally, baseball batters have been rated by their hit average - the proportion of times they go out to bat and hit the ball into play without immediately getting out. It's a number given to three decimal places, and an average of 0.300 ("batting 300") is normally considered very good. Unfortunately, it doesn't tell you much about the player's contribution to the game.
One of the things the geeks realised is that - unlike in cricket, where there's either a time limit or a fixed maximum number of balls in an innings - baseball innings can, in theory, go on forever. And as long as your players avoid getting out, you're scoring runs. (There are ways of getting to first base without hitting the ball.) More to the point: if other teams are focussed on picking up players with high averages, you can pick up some real bargains if you look for players who just don't get out.
Under Beane, the Athletics reached the playoffs frequently - while keeping their expenses relatively low (in 2006, they had the 5th best record in the baseball leagues, and the 7th-lowest payroll). However, as other teams cottoned on to the ideas behind the Athletics' success, the strategy's effectiveness declined.
I nominate Billy Beane as a Mathematical Ninja, not for his mathematical ability, but for his decision to listen to the geeks and for using statistics to completely change the way a sport was played. Even if the sport is an inferior version of cricket.
* You can read more about Billy Beane's statistical adventures in Moneyball: The Art of Winning an Unfair Game, by Michael Lewis. There's also a film with Brad Pitt in, but I haven't seen it.