Horizen (ZEN) is the native cryptocurrency of Horizen blockchain. It can be mined. Much alike Zcash, ZEN offers regular and shielded addresses. A number of exchanges feature ZEN, including USD as a pairing choice on Bittrex.
Nexus (NXS) coin is available on a few exchanges, including Binance. You can purchase NXS for BTC. This coin can be staked or mined and serves as the core cryptocurrency of the decentralized Nexus network.
Tether is a cryptocurrency launched in 2014. It is a so-called stablecoin currently leading by market capitalization. Although according to the initial idea, each Tether was backed by $1 (that was going to keep the price of Tether stable), the company not always managed to maintain this price (at some point in October 2018 the price dropped to $0.9 per one Tether). Tether succeeds in terms of market capitalization and its price is almost all the time is really close to $1.