The one I've always wanted to try is salt cod. Like made into a stew or some such. Curious what the big deal is about. Seems like a lot of work, though, buying it days ahead of time, soaking it and changing the water every 12 hours.
Tuna and salmon is where it's at. When I'm flush and it's in season I love to get some king salmon. Grilled on the half shell (skin side down, no flipping) with just some olive oil, garlic powder, lemon pepper, black pepper and dill until the color just whitens. Holy **** is it good. Like a stick of butter and a fish got together and had some crazy butter/fish sex.