I even prefer mustard on my potato salad.
When did mustard on a hamburger become sacrilege?
"Even"? "Sacrilege"? Yall aren't from the Hill Country, are you?
Nothing wrong with a little mayo if the situation requires (like in a really juicy burger, as noted earlier), horseradish+mayo on the bottom bun, lettuce, tomato, grilled onion, cheddar & bacon is a hell of a burger.
Anyone tried the Hawaiian sweet burger buns? When you're in the mood for something different, they work damn well, may not be for everyone though.
Also: cheese, American or other?
Also also: Cajun Power Garlic Sauce is a necessity in any respectable Texas pantry.