Commodity market
Whole developing nations may be especially vulnerable, and even their currency tends to be tied to the price of those particular commodity items until it manages to be a fully developed nation.  For example, one could see the nominally fiat money of Cuba as being tied to sugar prices, since a lack of hard currency paying for sugar means less foreign goods per peso in Cuba itself.  In effect, Cuba needs a hedge against a drop in sugar prices, if it wishes to maintain a stable quality of life for its citizens.