Zimbabwean dollar
A fiat-money currency greatly loses its value should the issuing government or central bank either lose the ability to, or refuse to, continue to guarantee its value. The usual consequence is hyperinflation. Some examples of this are the Zimbabwean dollar, China's money during 1945 and the Weimar Republic's mark during 1923. A more recent example is the currency instability in Venezuela that began in 2016 during the country's ongoing socioeconomic and political crisis.