i love cold, crisp pickles on their own, but on a burger they get warm and mushy and their sourness does not play well with the rest of the flavours
i also don't like raw tomatoes (will eat ketchup though), and i usually don't put onions on my burgers, though i will put them on hot dogs
on the other hand, lettuce is an ABSOLUTE necessity. any burger without lettuce is a bad burger. you need some freshness and crispness to contrast with the rest of the burger