Vanguard Energy Index Fund Admiral Shares 

This cost-effective index fund grants investors access to the U.S. equity market's energy industry, focusing on companies involved in the discovery and production of energy resources such as crude oil and natural gas. Its primary risk stems from this concentrated scope, as it exclusively holds stocks within the energy sector. Investors should anticipate substantial price volatility, making it most suitable as a minor allocation within an already well-diversified investment portfolio.