Hardee's has been gradually disappearing in my town as well, but honestly, I was never a fan of any of their food - I never really cared for that overly charred flavor their food has, even though I know that's basically their speciality: charbroiled food.
Otherwise, mustard is the only sauce that Krystal (the southern equivalent of White Castle) puts on their burgers, but you really have to be careful, because certain locations go as overboard on the mustard as McDonald's tends to do with their ketchup.
Meanwhile, if you get a burger at Sonic (talk about another burger that'll really sit in the bottom of your stomach), you get the choice of either ketchup, mustard, or mayonaise (I usually go with mayo).
Otherwise, mustard is the only sauce that Krystal (the southern equivalent of White Castle) puts on their burgers, but you really have to be careful, because certain locations go as overboard on the mustard as McDonald's tends to do with their ketchup.
Meanwhile, if you get a burger at Sonic (talk about another burger that'll really sit in the bottom of your stomach), you get the choice of either ketchup, mustard, or mayonaise (I usually go with mayo).