Brass and lead ... not a viable currency ... ever. (But still very good to have)
Gold, silver, and commodities. If equities and treasuries crash with all the leveraging going on. These will have a MASS SELL OFF and the prices will drop as hedged and leveraged firms attempt to raise capital to meet things like margin calls. If the currency completely collapses aka Weimar, or Zimbabwe, silver gets very valuable as a working medium of exchange along with the fact that most money is electronic. Deflation will be rampant as the supply of money will be extremely small in pre-collapse comparison.
Does it build or produce something and can you physically own it? That's a good buy. Firearms + ammo are good buys. Food, almost always fungible or tradable for someone's labor. 300 bucks of food can go a LONG way as wages for labor in a post collapse economy.
Those are my thoughts anyway.
I like sugar and molasses for barter goods. Can always turn them into booze.