There has been few bitcoin hard forks of bitcoin and more are coming. What they are? What are their purposes?
Bitcoin Diamond
Bitcoin Diamond implements anonymity or privacy feature which is not available in Bitcoin. It changes Proof-of-work to Proof-of-stake and supports SegWit. There will be 210 million BCD in circulation.
Symbol: BCD
Fork Date: November 24, 2017
Bitcoin Silver
Bitcoin Silver is a fork of bitcoin. Its purpose is to make Bitcoin mining decentralized again. It implements proof-of-work algorithm Equihash which provide an opportunity to new people to participate in mining with consumer hardware. SHA256 mining equipment will be obsolete for Bitcoin Silver. It has implemented full replay protection which is a feature that protects users coins from being spent accidentally.
Symbol: BTSI
Fork Date: December 2017
Super Bitcoin
Super Bitcoin is a proposed improvement to bitcoin. Some of features including lightning network, smart contracts, zero knowledge proofs and larger block sizes. There will be a total supply of 21,210,000 SBTC, with 210,000 being pre-mined.
Symbol: SBTC
Fork Date: December 17, 2017
Bitcoin Unlimited
Bitcoin Unlimited is not a hard fork to an unlimited block size but allowing users to signal which block size limite they prefer. It enables nodes and miners to agree/disagree with a change.