I don't know if it is zero risk, but I was looking at a system that employed selling naked puts on S&P stocks, looking at what % of the S&P those stocks make up, then buying puts on either the SPY or OEX ( I don't remember which) at a ratio that protected you from big downturns on the stocks and made $ on the difference. It required a fair amount of margin but the record he published looked pretty good and the math seemed sound.