Depends on the pizza. Toppers has this Tator Tot pizza that I dip nacho cheese sauce in. But ussally I don't dip or just use marinara sauce.

I know people who dip their pizza in ranch. I also experienced a friend dip their pizza in garlic butter, which I tried and didn't hate. These days I just sprinkle a little garlic salt over my pizza for flavor. As for the pineapple pizza debate, I've never been a fan of mixing sweet and salty or sweet and savory. I don't like salted caramel, I don't like nuts in my ice cream, and I don't like pineapple on my pizza. I want my sweet things and my not sweet things as far away from each other as possible. That being said, I've never been disgusted by people who enjoy pineapple on their pizza. I just politely request that half the pie be cheese or pick the pineapple off if I have to.