If you want stable value with no chance of droppng...
Forget crypto, there are no guarantees.
Forget fiat, it inflates continuously.
Keep something scarce with intrinsic value, like copper for example, or helium.
You are too pessimistic. ) "Forget" - isn't the best option. It can be created, decentralised, trustless and stable. With only private key as a proof of ownership. BitShares assets - was the first try, but there are some flaws too. Need to look into smart contracts with SideChains and decentralised data feeds. I am sure there are some developments happening right now.
No any scarce resources can be stable in long term, as there is always demand fluctuation and speculative component of price.
http://www.kitconet.com/charts/metals/base/spot-copper-5y-Large.gifAnd keeping physical metal under bed is not actually what I am looking for, but any derivative with centralised issuer has trust questions.