I seem to feel quite strongly about these in the face of the masses who don't seem to mind either way.
  1. Mustard on a hamburger or cheeseburger.
    Ketchup I can abide for others, but would never have myself. Mayonnaise is perfectly fine.
  2. Ketchup on a hotdog.
    Mustard please, and raw onions. Hot mustard and sauerkraut for a bratwurst.
  3. Pineapple on a pizza.
  4. Plum sauce on a duck.
  5. The "a l'orange" on duck a 'l'orange.
    Outside of Thai duck curry with pineapple, fruit and meat combos are out for me. Hence the following...
  6. Turkey with cranberry sauce.
    How can you taste the turkey when it's swimming in that?
  7. Lamb with mint.
    See above.
  8. Chocolate with orange.
    Or chilli, or mint, or just about anything except the odd whole nut, rice crispy, or caramel.
  9. Chocolate liqueur.
  10. Prosciutto and melon.
    Buffalo mozzarella wrapped in prosciutto? Bring. It.
  11. Raisins in just about anything - but particularly brownies and cinnamon buns.
  12. Jam in a donut (see #6).
  13. Anything other than powdered sugar on a funnel cake (yes, including lemon juice).