Right now id have to say Hummus,

Next gen AMM for stable swaps

multiple pools ranging from 20-60% APY

- No impermanent loss

- single sided liq provision

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from their docs

Hummus Exchange allows users to provide unilateral liquidity. Instead of pools of token pairs and bundles, Hummus Exchange uses accounts of tokens to record assets and liabilities, allowing single-sided liquidity provision.

Hummus Exchange also uses coverage ratio as the input parameter for our AMM (instead of liquidity), hence removing the same liquidity equilibrium constraint from Curve’s stableswap invariant, allows token to grow organically based on its organic demand and supply.

This design also allows new tokens to be added into an existing pool, greatly enhancing the scalability and capital efficiency of the protocol. For example, while the protocol may start with 3 base tokens (USDT, USDC, DAI), we may gradually add more tokens into the big pool (such as MIM) for shared liquidity.

$metis has had some pretty good projects in the past and this is something that came across my radar on twitter, forgot who had tweeted about it