Exchange-traded funds (ETFs), otherwise known as investment funds that are traded on stock exchanges, are commonplace in the investment world. However, because of the current volatility in the cannabis sector, there isn’t an abundance of marijuana-related ETFs. Horizons Marijuana Life Sciences ETF (OTC: HMLSF) is a rare cannabis-related ETF, and it could be a sleeper power play this year that some investors aren’t thinking about.