You actually have some decent options, depending on tank size and what kind of water your looking to keep. If its a very large tank and coldwater isn't a problem, bowfins, gar, sturgeon, and various forms of native fish often get attention. If you're looking for fw tropical, i would definately recommend a big electric catfish and also lungfish. Walking catfish are pretty unique as well, dont know if theyre around anymore however. The most eye catching option would be a brackish, mangrove type setup. There are all sorts of oddballs out there, Anableps anableps, mudskippers, dragon gobies, brackish morays, etc. Good luck on your tank setup!