Exchange-traded funds (which are essentially mutual funds that can be traded like stocks) have offered investors unprecedented access to the financial markets. As ETF assets continue to grow, issuers are forging into increasingly unfamiliar territory. While these ETFs have unprecedented themes, they also can have unprecedented risks. Many of the more complex and nontraditional ETF strategies are appropriate for only sophisticated investors. Nontraditional ETF funds that invest in derivative contracts like futures have been the subject of regulatory scrutiny in recent months. Funds that use leverage to achieve their goals are inherently more volatile than unleveraged ETFs and are designed with sophisticated investors in mind. Leveraged ETFs can be caustic in the hands of long-term, buy-and-hold investors who do not understand their strategies completely. These "10 Most Dangerous ETFs" are funds that are not for the average buy-and-hold investor. As always, potential investors should examine each fund with an eye toward their own goals in order to determine suitability.