I'll name one: Monero. It's not a fork of Bitcoin. It's based on CryptoNote. Unlike Bitcoin which is public and traceable, Monero's address balances are private and the transactions are not traceable. It is fairly mined (no premine or instamine).

There's a lot of interesting tech/code behind it. Check out the Monero subreddit and/or start here: https://www.monero.how/

I learned about Monero when someone else mentioned it in a comment here on HN earlier this year. After doing my own research, I believe Monero was and still remains the best solution available to fulfill the requirements of a decentralized digital currency.