I don't eat hamburgers from any burger joint EXCEPT for In N Out Burger. Smart choice on my part, I'd assume, given the comment stream above. Chicken sandwiches 4 lyfe!
As for me, anything that has...well, any condiment for the most part I cannot stand. I heavily dislike, hate even, ketchup/catsup, mustard, mushrooms, brussel sprouts (spelling?), mayonnaise, and many MANY others. I just can't take that stuff, it's disgusting. When I get a hamburger be it from In N Out or homemade, I get a patty and a pair of buns. I put french fries and barbecue sauce in between the meat and the bun, because they're almost a triplet, but nothing and I do mean NOTHING else. Onions sometimes I can tolerate, only sometimes.