Snake oil, its the future; and I can get you 100Ks worth easy.
Seriously though, this is a dumb question. There is no such thing as guaranteed returns, and anything with a 20% return probably has inherent risks that you don't appreciate, or is completely illiquid. If you want to invest money responsibly and you don't know how, then speak to a financial advisor -- that's what they're there for.
Not a dumb question at all. Many advisors are highly paid risk-takers with your money, that have their own bottom line as their main interest. Knowledge is always helpful to protect any investment.
That being said, are you thinking shorter term or longer?
I mostly look for cash-flow kind of investment rather than future appreciation - so if I invest in real estate then in 5yrs I get my money back ... I dont expect with solid similar option but anything with 5yrs timeline should be good enough.
Seriously though, this is a dumb question. There is no such thing as guaranteed returns, and anything with a 20% return probably has inherent risks that you don't appreciate, or is completely illiquid. If you want to invest money responsibly and you don't know how, then speak to a financial advisor -- that's what they're there for.