Bitcoin and cryptocurrency at the moment
"A wash trade (not to be confused with a wash sale) is a form of market manipulation in which an investor simultaneously sells and buys the same financial instruments to create misleading, artificial activity in the marketplace.[1] This may be done for a number of reasons:
To artificially increase trading volume, giving the impression that the instrument is more in demand than it actually is.[2]
To generate commission fees to brokers in order to compensate them for something that cannot be openly paid for. This was done by some of the participants in the Libor scandal.[3]
Some exchanges now have protections built in, sometimes mandatory for participants, such as STPF (Self-Trade Prevention Functionality) on the Intercontinental Exchange (ICE).[4]"