Rob Wolf has raved about this tuna from Portugal packed in virgin olive oil.  Now that I have tried it, I agree.

This tuna is a solid piece packed in olive oil. It is rich and mellow in flavor; would be great in a salade nicoise, and it’s wonderful straight out of the can. Ingredients listed are tuna, olive oil, and salt. The label indicates 1.5 servings per can at 160 calories, 11g fat, 370mg sodium, 14g protein and 0 carbs, fiber, and sugar per serving. It’s a simple matter to drain the oil away since it’s a solid piece of tuna. It’s a product of Portugal, distributed by Italy. This is the best mail-order price I’ve found anywhere; you can easily pay double for it from other purveyors. Very highly recommended.
What is even better is this tuna is caught by  Pole-and-line in small batches.