Laser Beam
Beam added relative kernels (e.g., kernels that are only valid if another kernel exists on the blockchain) as a part of our expansion of the Mimblewimble protocol, which birthed the creation of Laser Beam direct payment channels similar to those used in the Lightning Network.
Fast transactions and scalability is an issue that most cryptocurrencies have yet to solve. Laser Beam establishes a funded channel between two wallets that performs instant transactions that later settle on-chain. Laser Beam is operational on Beam Mainnet (Command-Line support, only).
See our Beam wiki for more information regarding Laser Beam.