How big is your tank?
A marine betta, for instance, might or might not fit . . .
Dottybacks also love to weave in and out of the rockwork, but not all play well with others.
My dwarf angelfish spend a decent amount of time under overhangs and in between rocks, but not in the deepest of caverns.
Royal grammas (and the closely related black-cap basslet) will generally choose a cave and stay fairly close to home, as will many gobies.
~Bruce