Editor's note: This is the first of a two-part series on the 10 best ETFs.ETFs have helped investors gain unprecedented access to niches of the marketplace while mitigating the security-specific risk that comes with stock-picking. The best exchange-traded funds use the unique capabilities of the ETF structure to their advantage and offer unique strategies at reasonable prices. Last week, I counted down the 10 Most Dangerous ETFs in an effort to alert buy-and-hold investors about the risks of certain funds. Here are Part 1, Part 2 and Part 3 of that series. Today and tomorrow, I will be counting down the 10 best ETFs. These funds live up to their promises and demonstrate the capabilities of the growing ETF universe. Here are nos. 10 through 6. 10. Vanguard Emerging Markets Stock ETF ( VWO) VWO is an excellent example of the benefits of increased competition in the ETF space. This fund tracks the same index as the iShares MSCI Emerging Markets Index (EEM), but does so at a lower price. While VWO has a lower trading volume than the older EEM, it is still more than high enough to ensure liquidity for the average investor. An emerging markets position helps to diversify a portfolio and provide access to commodities plays. While VWO is one of the broader-emerging market offerings, it is a good place to start. 9. Market Vectors Coal ETF ( KOL) KOL is a good example of a narrowly themed fund that helps investors target specific areas of interest in the marketplace. KOL tracks the Stowe Coal Index, which provides exposure to publicly traded companies worldwide that derive greater than 50% of their revenues from the coal industry.