Tornado Cash

Tornado.cash helps you to reclaim your privacy. You can use it to send Ether to any address in a way that obscures your sending address.

It does this using zero-knowledge proofs. You can use this app to deposit some ETH into a non-custodial smart contract, and then easily generate a proof that you had perfomed said deposit without revealing your original address. The app will then send this proof to an operator, which will submit it to the smart contract, which will in turn send the ETH to the desired recipient and reimburse the operator a small fee.