If you like mayo then use a little bit of mayo. It's only bad for you in large quantities and if you eat it all day everyday. I use just a little bit to trick my tastebucs into thinking it's really there. But for more flavor I also put in a little bit of spicy mustard and a spoonful of relish. It adds a lot of flavor.
Word of caution. Beward of anything labed fat-free. It's loaded with sugar. There is no such thing as fat-free mayo, it simply does not exist in nature and it is concocted in a chemistry lab... the last place food should be prepared.
I use a bit of sour cream to hold it together, and lots of pickle relish and/or mustard (I actually sometimes buy a pickle relish that has mustard in it).
This thread has so many good ideas for my tuna that I can't wait to try. I normally eat it with some kind of mustard (I do love my mustard) but sometimes I'll eat it with salsa too. I'm thinking I might have to get adventerous and try both now.
There are a lot of responses to this and I just don't have the time right now to read through them all! But I wanted to chime in with my favorite way to have tuna, in fact I ate this just yesterday!
1 can tuna
1 wedge laughing cow cheese
somewhere around 1 tsp to 1 tbsp of mustard (my favorite is sweet and hot mustard)
chopped onion
chopped bell pepper
chopped dill pickle
liberal amounts of ground black pepper
I love it with lemon on it. But it has to be fresh squeezed lemon. About a half one does it usually. I can't stand the bottled stuff...I also make sure I get the good stuff (tuna), not the cheap stuff...it just tastes better.