Proof of Stake
Consensus where the right to create blocks is allocated by how much capital you have locked up, not by how much electricity you burn.
Validators deposit a stake and are then selected to propose and attest blocks. Misbehave — signing two conflicting blocks, going offline — and you lose part of the stake through slashing. Security therefore rests on attacks costing your own stake rather than costing electricity.
Ethereum switched from proof of work in September 2022, cutting the network's energy consumption by over 99 per cent. The objection to the model is that it can reinforce concentration: whoever holds most earns most and can lock up still more. The 32 ETH requirement for running your own validator has additionally made staking services dominant.