The stock market is full of unproven, speculative stocks that aren't suitable for the average investor. However, if you're aware of company-specific risks and willing and able to accept the consequences, speculative stocks can occasionally turn out to be big winners for a portfolio. With that in mind, the Fool's health care bureau chief, Brenton Flynn, outlines two of 2013's best-performing (and speculative) stocks in the industry and offers a few words of caution to prospective buyers.