Jason Zweig wrote an article for the Wall Street Journal titled The Safe, High-Return Trade Hiding in Plain Sight.
An I Bond is an “inflation-protected U.S. savings bond… yielding over 3.5%, nearly risk free… The maximum purchase is $10,000 per year per account holder… Unlike with Treasury inflation-protected securities, or TIPS, the yield on I bonds can never go below zero. So they protect against both inflation and deflation, which is pretty amazing.”