It totally depends on the sandwich. If it is beef, mustard. Chicken, mayo. Turkey, Durkee Sauce. Ham, mustard again. Hot dogs...cheese and onions. If I'm making a "salad" sandwich, chicken, egg, etc, then mayo. And it has to be Kraft or Hellman's. Both of those are tangy. I LOATHE a bland mayo. NEVER EVER Miracle Whip. Nasty stuff. I love horseradish when I'm having bologna, which is rare. And a little with roast beef is good, too.