[dumbfoundded]

Monero & Zcash are the best examples right now but like bitcoin, they are volatile and not practical for actual commerce outside of use-cases (like crime) where it's worth the cost.

Stablecoins are a large use case in crypto now but there isn't a private stablecoin yet (I'm ignoring all SGX based technology). A private stablecoin, fully backed by audited bank reserves would enable something like a private Venmo. This private Venmo would know how much you brought in and took out but would have no idea what your transaction history looks like. I think in the next few years we'll see a private Venmo.