BitcoinDark is a fork of Bitcoin with a poorly defined purpose and use case. BitcoinDark is based on the InstantDEX protocol, a decentralized exchange for BitcoinDark and other cryptocurrencies supported by the project. The platform is also supposed to include a Pegged Asset Exchange (PAX) to allow users to buy and sell pegged assets – including fiat currencies, commodities, ETFs, and stocks.
BitcoinDark is a Proof-of-Stake (PoS) currency that has gained a significant market cap, but the project has failed to show how its vision will be implemented or how it will add value compared to other blockchain projects.

GAS is the token that is used to pay for transaction fees on the NEO network. The NEO platform uses two different tokens; GAS are used to fuel the network and give holders the right to use the NEO blockchain. Similar to Ether on the Ethereum network. Although it's possible to buy GAS on some exchanges, NEO token holders automatically generate GAS as the blockchain increases in size. 8 GAS are distributed for every 100 million NEO in circulation.

.

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.