don't want to throw off on the gold bugs or the silver hounds, but to add another coin / metal for consideration in your bag of tricks perhaps in addition to gold or silver:
A Nickel has almost 7 cents (at today's prices) of copper/nickel.
It is the only US coin now in general circulation (other than older pre-1982 pennies and pre 64 silver dimes and quarters - good luck finding any of these) that you can readily acquire.
They are easy to acquire - no mail order just go to your local bank. I get them $20 at a crack.
They are cheap to acquire in small batches - you can get a roll of nickels for $2, or just save the ones you get in change.
If we were post SHFT right now and trading at coinage metal content value, a nickle would be 7 cents, a silver dime about a 2 dollars, and a silver quarter about $5, so nickels might fill the low end barter transaction nicely.
when a government stops making "pure" coins that have historically been minted, and starts issuing "hollowed out" coins like the current penny, dime, quarter the older pure coins immediately increase in demand.
Nickels cost the US mint almost 10 cents to produce, so how long do you think they will keep that up?
also historically when a currency is devalued because of hyper inflation the normal course of action is to issue new PAPER money and all old paper money must be exchanged for the new paper, but rarely are coins exchanged. I guess the reason is that nobody figures that the peasants have much in real coins other than the change jar and also that the task of receiving in all the coinage would weigh as much as a battleship, so it just isn't done.
so suppose we fall prey to hyperinflation and the Federal Reserve decides to lop off a zero or two from the currency so that a $100 is exchanged for a new $1 bill - your nickle just jumped in purchasing value by 100X, effectively making each nickle worth $5.
the real downside is that nickels are bulky. When I get $20 of nickels it is a fist full for each hand!
the other downside is that you get some pretty weird looks by the bank tellers when you ask for $20 of nickels and nothing else, but there are so many bank branches around that I can go a couple months between visiting the same one.
there is no downside, you can't loose money on this investment, you can always take that roll of nickels back to the bank and get some of that safe folding money!