There are quite a few, but off the bat:
  1. Payment Pools represent a technique for CoinJoins with "lazy output creation" where the pooled funds can be kept as a single coin which does iterative (on-chain) updates to make payments on-chain. Update data only has to be shared with your hierarchical neighbors with CTV, so you get some better privacy v.s. other techniques.
  2. PathCoin is a novel concept for a coin that is off-chain transferrable amongst a group of N users with only the sender/receiver (2) having to communicate (v.s. lightning which requires N of N online)
  3. Non-Interactive Batched Lightning can make channel opening hidden until close, with opportunity for cooperation (pairs with Payment Pools)