Mine usually consists merely of a packet or can of tuna(I'm not as picky as Izzy on the whole oil vs water question), about two good tablespoons of sweet relish(the only use I've ever found for the otherwise vile ingredient), and of course a good dollop of mayo/salad-dressing.
If I have the ingredients around, I'll sometimes add some finely minced celery, or alittle ginger, or some onion, or even alittle minced garlic. Of course, I'm one of those people who could add garlic to Fruit Loops and be in heaven, such is my love of the stuff...