DigitalNote (XDN) cryptocurrency is currently listed on the number of exchanges against cryptos (BTC or ETH). It emerged in 2015 as a Fair Launch, which did not imply any reward for developers, ICO campaign or premined blocks . Recently, XDN held a swap to the XDN 2.0 network with improved functionality.
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.
THEKEY (TKY) is the token of the Chinese government endorsed blockchain based identity verification ecosystem. The token is currently based on cryptocurrency NEO protocol. It is listed on a few exchanges paired against major crypto coins.