If you are concerned about a crash, stocking up on bullets, beans, canned goods, water filters, gasoline - those things are invaluable and are worth something to nearly everyone.
What if silver and gold is outlawed?
Be able to provide a service to others as trade. (Not everyone looks pretty and sexy, so I'm not talking the obvious!) Have tools and materials on hand, and the knowledge to use them. Welding, plumbing, auto engine repair, carpentry, electrical know-how, babysitting, etc.