While living on Cranbrook's campus, I created The Cave, which was a general store and smoothie stand that had its own currency, Lithium (theoretically backed by a lithium-carbonate standard, which was also an ingredient in our Calming Smoothie™). Our most in demand/illicit items were only sold in the currency, and every other item had a discount applied if Lithium was used. By the end of The Cave's run, Lithium was being exchanged among students and was accepted as payment at the on campus student lounge.
The Cave / Lithium
lithium carbonate, currency, smoothies