I can actually think of something that isn't good with peanut butter. Cheez Its. That was some terrible stuff. XD
I always had school pizza with ranch, but I can't picture my self doing it with my home made pizzas. No need to add extra flavor when the crust is already mixed with various cheeses and spices... that's some good crust...
On unusual combination I do (assuming the Ranch is good, my parents like to keep the same bottle of Ranch in the fridge for years at a time) is Ranch and Tortilla chips. That... that's just amazing, I can't even describe it.