When I make tuna, I use the solid white packed in water, drain as much as possible, and add dill relish and mustard until it is almost the consistancy I want. Once I've managed that, I add about one tablespoon of light or fat free mayo. This gives the creamy texture I crave from tuna, but packs a lot fewer calroies.
To change up the flavors I may skip the relish, increase the mustard, and add a no salt seasoning blend before I add the mayo. Play around and see where your taste buds lead you