Thanks, clothier, for your explanation. The more I've thought about it, I've decided I'm a traditionalist when it comes to burger toppings, so I may take a pass. Anyway, I've just found a place that does a pretty good muffaletta, so I'm gonna stick to that and popping stuffed Queen olives straight from the bottle

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Wellllllll, I was going to say, the local branch of the Hamburger Toppings Institute won't release their latest data

, butttttt, judging by the advertising for the FF chains, 'Texas style' means 'mustard and extra pickles.' That includes JIB, McD, BK and Wendy's; I don't know what Sonic puts on their burgers. The standard dressing on a Whataburger is mustard.
As for non-chain places, I don't know how anybody can sum it up, with so many places to choose from.
I never had ketchup on a burger until I had my first Quarter Pounder w/cheese at McD ca. 1973. I prefer sliced tomatoes, tho they're usually so tasteless I can understand the use of ketchup.
Mesquite grilled patties are fairly common around here. Salsa or Pico de Gallo are offered at a number of places as toppings (I think they have about as much place on a burger as ketchup).
Can't remember now the other stuff I was so frustrated trying to post last night, but I'm thinking of starting a 'specialty burger' thread; there are a couple of interest locally and I've heard others elsewhere.