The Horn-nosed Boxfish (Ostracion rhinorhynchos) grow to about 14 inches in length and inhabit the waters East Africa eastward through Indonesia to northern Australia and as far north as southern Japan. They have no real commercial value.
I personally like the Pacific lumpfish (adorable, to die for), but I also love a lot of the ones people have posted (Locariids, Mormyrids). It's true, there are just too many to choose one!