For fish, I'd probably go with frogfish.
For inverts, my dream's nautiluses.
Another I would consider are one of the Eusocial Snapping Shrimp species (Synalpheus spp.; Synalpheus regalis is the best known, but there are reportedly a couple other species from the genus which exhibit this behavior as well) - these form ant-like colonies with one reproductive queen and several "workers" in the colony; they also live inside of and defend a home sponge.
And, there's also the Semi-terrestrial Shrimp species (Merguia spp.; M. oligodon and M. rhizophorae) which can climb trees and hop away from danger - these would be cool to setup a paludarium for.
For inverts, my dream's nautiluses.
Another I would consider are one of the Eusocial Snapping Shrimp species (Synalpheus spp.; Synalpheus regalis is the best known, but there are reportedly a couple other species from the genus which exhibit this behavior as well) - these form ant-like colonies with one reproductive queen and several "workers" in the colony; they also live inside of and defend a home sponge.
And, there's also the Semi-terrestrial Shrimp species (Merguia spp.; M. oligodon and M. rhizophorae) which can climb trees and hop away from danger - these would be cool to setup a paludarium for.