BitcoinZ
Like BTG, this currency appeared in October 2017, so it is too early to judge its success. Unlike the above "bitcoins," BTCZ is not a fork of BTC, but of another currency - Zcash (ZEC).
BitcoinDark
Unlike BCH and BTG, this is a relatively old currency. It appeared in the times when BTC was faithful to Satoshi's principles in 2008, had no particular problems with speed and was criticized by few people.
Bitcoin (updated, from August 2017)
This currency is considered an official continuation of the original BTC, although technically it differs significantly from it. In August 2017, SegWit technology was added to the BTC algorithm, allowing some transactions to "bypass" the currency's blockchain.