By Michael Johnston, founder of ETF Database.The S&P 500 is one of the most widely followed benchmarks in the world, a bellwether of the U.S. economy that is included in the Index of Leading Indicators. Composed of 500 of the largest stocks listed in the U.S. (as well as a handful of non-U.S. companies), the index has a weighted average market capitalization of approximately $80 billion and includes companies across all sectors of the economy. With the rise of indexing as an investment strategy, it's not surprising that exchange-traded funds designed to track the S&P 500 are among the largest and most heavily traded ETFs. With a market capitalization of more than $57 billion, the SPDR S&P 500 ( SPY) is by far the largest ETF, nearly $20 billion larger than its closest competitor. The iShares S&P 500 Index Fund ( IVV) comes in at No. 4 on the list with almost $21 billion in assets, meaning that U.S. investors have nearly $80 billion invested in S&P 500 ETFs. Although the SPY and IVV are by far the most popular ways to play the S&P 500, they're not the only games in town. There are a number of exchange-traded products that offer similar risk and return profiles but also feature twists that in some cases allow them to outperform the popular benchmark by a wide margin. ProShares Credit Suisse 130/30 ( CSM) This ETF employs a 130/30 strategy that has been popular with investors for some time but is new to ETFs. The CSM tracks the Credit Suisse 130/30 Large-Cap Index, a benchmark that establishes either long or short positions in S&P 500 equities by applying a rules-based ranking and weighting methodology. This fund essentially establishes a 100% long position in the S&P 500, then sells 30% of the value of the portfolio in holdings that are expected to underperform. It then uses the proceeds of those sales to establish long positions in holdings that are expected to outperform.