My favourite invention in crypto is Uniswap range orders. Most crypto apps are alternatives to stuff that have existed, but Uniswap range orders are largely unique, offers a great way to scale in and out of positions, and earn while you're doing it! That and ZKPs as a broader category, of course.

interested in any zk privacy projects? there seem to be a lot in development rn

I haven't been following, any recommendations?

namada; a multi asset shielded pool for eth and cosmos tokens

penumbra; shielded ibc dex 

zcash; moving to hybrid pos and adding tokens

railgun; private eth L2