If you are sick of the regular tuna sandwich with mayo, here is an idea to add a kick to it:

I like to use dill dip from Wildtree and mix that with the tuna.  Once the tuna is on the bread, spread some sliced cucumbers on top and then top with some cheese (if you like) and add the bread.  You get a nice crunch from the cucumbers and the dill adds in a some flavor.

Enjoy!