I like to rinse my tuna so its not quite so fishy, and throw some sliced cucumbers and/or chives in with pepper and/or Mrs. Dash (garlic & herb..hmmm) - I find that alright to get down. Cucumbers are good because it really moistens it up and makes it alot easier to swallow.
Yeah eating regular Tuna out of the can gets old quick. All I did was switch from the reg. Tuna to the Albacore which in my opinion taste a hell of a lot better. But there are some good suggestions here.