If it swims, flies, slithers or crawls it can be smoked. Some just easier than others...... Not sure what part of the world you are from, so I would try anything that is locally caught. Do a search for things close to it here and play with the recipes to suit your needs....
Some of my favorite as a kid growing up was smoked mullet....it is amazing..... oysters and clams are a bit tricky, but very good..... you have your main stream meats like dear, elk, cow, chicken, pig, turkey, boar, duck, etc...... then you have your not so main stream like possum, coon, snake, squirle, etc....... try them and let us know what you find out....we love to share and see pictures...