French Fries with things other than Ketchup - I know we're not the only ones, but dipping French fries in a Wendy's frosty was big when I was a teen. Mayo, cream gravy, Cane's sauce, tartar sauce, and remoulade are also high on my list.
Cake combos - I went through a phase where I was making odd combos. Maybe I'm more grateful for the people willing to try them, but the avocado pound cake with bacon brie buttercream really stands out in my mind.
Bacon and anything sweet - I made bacon candies one time. They were good. Some where just straight chocolate dipped bacon, but others involved things like apricot and brown sugar.