Last time I had tuna, I had it as a sweet potato tuna melt. I mixed the tuna with cottage cheese and salsa, put it on top of half a baked sweet potato, topped it with mozzarella, and then broiled it for a few minutes.
I also like making tuna burgers with onion, a tiny bit of mayo, an egg, some oats, and some spices. Depending on what veggies I have around, I'll throw in some peppers, or celery, or something. Then I just fry it up in olive oil.
I used to love mixing tuna and hard boiled eggs with mayo, topping a half a hamburger bun, and putting cheddar on it and baking it that way, but I try to keep my grain consumption fairly low. Though now that I think of it, I might try that combo on a sweet potato.