PIVX is a cryptocurrency that is focused on privacy, speed, and low transaction fees. It was originally called Darknet and was forked from DASH. PIVX has a strong focus on community governance.
PIVX (Private Instant Verified Transaction) uses a privacy-centric Proof-of-Stake consensus protocol that allows anonymous staking.

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.

Stealth is a cryptocurrency focused on privacy and and speed. The Stealth blockchain has a Quantum Proof-of-Stake (qPoS) consensus mechanism that is designed to enable almost instant transactions with improved privacy. Validators on the network are assigned a short quantum of time to validate transactions. The protocol combines two types of blockchain ledgers, for different types of transactions, to improve validation speeds on their platform. The network is powered by the XST coin.