Freicoin
Freicoin is "Bitcoin with demurrage".
It is an alt chain with the design goal that holders of the coin will have negative interest rates, as a means to increase the velocity of money by reducing the incentive to save. Fees are taken for holding coins and distributed to miners.
FAQ
Why would someone choose to hold a Freicoin and incur demurrage, where he can just hold Bitcoin instead?
Assuming they already have the Freicoin, exchange fees to Bitcoin may be greater than the loss from demurrage.