Unobtanium is a Proof-of-Work (PoW) cryptocurrency that uses the SHA-256 hashing algorithm. It was designed to serve as a commodity and store of wealth that would be less vulnerable to price fluctuations. The coin's supply is limited to counter inflation, and UNO coins were distributed in a manner that would discourage centralization. UNO can be merge-mined with Bitcoin.

Primecoin is a cryptocurrency based on finding prime numbers. Identifying prime numbers plays a central role in cryptography. Primecoin's unique Proof-of-Work (PoW) consensus mechanism is able to increase transaction speeds and improve energy efficiency.
The network searches for special prime number chains known as Cunningham chains and bi-twin chains, which are of interest in mathematical research.

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.