Sometimes I like just a plain burger with Miracle Whip, yellow mustard, and a little ketchup on the buns, then topped with American cheese, dill slices, onions, tomatoes, and lettuce.
I LOVE guacamole burgers.
I had a great burger at a little place in Riverside, California that had green olives cooked in the burger patty.
If I am cooking them on the stove, sometimes I add a little Worcestershire sauce, or I will sprinkle a little liquid smoke on them as they cook.
Once in awhile I will put an onion slice or a piece of cheese in the middle of the patty before cooking, just for something different.
Barbara