Let's say central banks will continue to print money and keep rates at zero or below, then what is the worst investment? It's cash. If you are really bearish about the world, then you don't want to be in cash, you need to invest.
Oil
There is a real danger that oil could go up substantially, maybe not immediately, but in the long run,
Bonds
Everybody says they hate bonds. The 10-year Treasury yields 1.74 per cent, which is very low, but compared to Japanese and Swiss bonds it's relatively attractive. US government bonds still have upside potential, especially if the US Fed continues to implement lower and lower interest rates.