Bitcoin Gold (BTG) is a cryptocurrency that began in 2017 as a hard fork of the Bitcoin blockchain. BTG was created to reduce the monopolizing power of dedicated ASIC mining operations within the original Bitcoin network. Bitcoin Gold mining can be done by anyone with a standard computer and provides greater decentralization to the system. The hard fork that created BTG was meant to combat the disproportionate influence and competitive advantage of professional miners.

ZCoin is a privacy focused cryptocurrency built on Ethereum. The ZCoin protocol enables anonymous transactions with cryptography that utilizes Zero-Knowledge Proofs (ZKP). ZCoin increases privacy on their network by using a coin-mixer contract that wraps transactions in a serial number and destroying wrapped coins once they have been redeemed.
Zcoin was the first cryptocurrency to use a Merkle Tree Proof (MTP) as its proof of work algorithm. Merkle Tree Proofs are an innovative solution to achieving network consensus, and can increase transaction time while reducing the centralizing tendency of ASIC mining.

FREE Coin is an Ethereum-based token with a focus on being inclusive and encouraging cryptocurrency adoption. Their goal is for the token's price to increase in value, until its price is close to the USD. FREE Coin's site does not provide any details about their development plan or what specific advantages their network will provide.