Hush is a cryptocurrency and messaging protocol that is focused on privacy. It uses a the equihash mining algorithm, which is a Proof-of-Work (PoW) consensus mechanism. It offers a high degree of privacy, and allows users to transact and send messages anonymously.
Hush is a fork of Zcash, and uses zk-SNARKS for zero-knowledge cryptography. Hush will allow developers to deploy Ethereum smart contracts on the Hush network.
The founders of Hush are closely associated with Komodo.

Grin Coin is a community driven blockchain project that aims to create a lightweight mimblewimble blockchain that will enable anonymous transactions. Grin has a Proof-of-Work consensus mechanism. Transactions are executed while hiding addresses and amounts.

Horizen, formerly called ZenCash, is a cryptocurrency focused on privacy. Horizen has an end-to-end-encryption system with zero-knowledge technology, that allows for anonymous transactions and messaging.
The company suffered a 51% attack in June, 2018 and has since re-branded as Horizen. Horizen hopes to combine anonymous transactions and messaging with an emphasis on community governance.