It would have to be ketchup, right? Versatile, sweet, savoury, and it can hide a multitude of sins. It would be hard saying goodbye to brown sauce for bacon sandwiches alone (though I don’t mind ketchup on a bacon sarnie), as well as mustard (all kinds) and any sauce of hot sauce. That’s really tough.
My mother claims I have the tastebuds of an old man who’s been smoking woodbines all my life (aka paternal grandad), because of my love of hot sauce and adding black pepper to things. She doesn’t like spicy food or even flavoured crisps though.