Invest in baseball player futures
You can play fantasy baseball for real now: there's a company that will sell you, as an investment, a percentage of a player's future income. If he becomes the superstar you think he will, you get rich. If he languishes in the minors, you lose.
Today, Marginal Revolution points to an investment opportunity on Indians prospect Randy Newsom. For $20, you get a claim to 0.0016% of Newsom's future salary. If Newsom earns more than $1.25 million over his career (discounted to today's dollars), you make money.
Actually, Newsom owns the company that you contact to make the deal. He's trying to make this work as a viable business, but right now he's the only player available to invest in. David Laurila of Baseball Prospectus interviewed him a couple of days ago.
This strikes me as a great way for prospects to buy a form of insurance on their careers. It's also a way for fantasy players and baseball fans to put their money where there mouth is.
The interesting thing is how this is legal, but would be illegal if it were anyone else trying to sell a percentage of Newsom's salary as a bet. If MLB and the MLBPA wanted to legalize this kind of gambling (there's probably no reason they would, but IF they did), they would agree to sell 1% of each player into the market. If that wouldn't be enough liquidity to meet fan demand, they could then issue futures contracts that settle in cash.
And, there you go! David Ortiz futures would be as legal as corn futures.
UPDATE: According to this Slate article, your payoff is based on Newsom's *after-tax* income. Plus, there are fees on top of your $20. It looks like Newsom has to make about $2.5 million, not $1.25 million, for you to break even on the deal. As they say, be sure to read the prospectus before investing!