Most investors are content to sit back and let their investments grow over time. Others love the roller-coaster ride of sharp ups and downs that come with more aggressive investing. These risk-lovers are willing to accept the chance of failure and loss in exchange for the very real (but hard to pin down) possibility of enormous returns.

Risk lovers have two basic ways to capture these sky-high returns: by investing in unusual and complex securities, or by using aggressive and chancy investment strategies. Alternative investments include things like IPOs, commodities, currencies, options, and futures. Alternative investing strategies include short selling, margin buying, and hedging. Aggressive investors can employ both methods to ramp up portfolio returns, though even the most risk-friendly investors keep a generous helping of safer buy-and-hold securities among their holdings as a safety net against total loss.

That's what the risk is here: total loss. At best, that means losing every dollar you invested. At worse, it means losing even more than you invested (and, yes, that can really happen). But for some investors, the gamble is worth it, and this type of investing gamble gives them the same rush they'd get by going to Vegas and putting it all on red.