Everyone has their favorite way to make tuna salad. This is mine.

tuna, white or albacore in spring water
hard boiled egg, chopped finely
2 or 3 tsp. cream cheese
mayo
dab of dijon mustard
shake of salt and pepper
1/2 -3/4 of an apple, chopped without skin
small amount of onion, preferably vidalia, finely chopped
a bit of chopped celery, not tons of it

Mix it all together.
You have to really smoosh the cream cheese into the tuna.
Don't buy a mealy or soft apple--you want a nice hard one, kinda sweet.

Sometimes I slice a few green olives and place them on top of the tuna once I put the tuna on the bread. The main thing that makes this good is to add cream cheese to whatever ingredients you use. Oh, and because you have the cream cheese, you still need the mayo, but you won't need as much mayo as with normal tuna salad.