There are many. Including mayo on a breakfast egg sandwich.
Then there's this lettuce and tomato on a hot sandwich thing. http://www.thedailymeal.com/eat/no-sa...
I will admit, contrary to part of the article, sort of, that ripe tomato on grilled meat sandwiches does nice work. But never, never lettuce on a hot sandwich.
No lettuce on a hamburger sandwich. No lettuce in a souvlaki pita sandwich or gyro pita sandwich.
So much so that I squirm each time I see a lettuce salad with hot chicken on it.