I'm not a fan of sweet stuff on a pizza. Pizzas are not meant for sweet stuff. Once something sweet, aside from pineapples, is on it, then it ceases to be a pizza.
I can't stand those "pineapple of pizza" type people (sorry Americans!). That just doesn't float my boat in the slightest!
I also don't eat any kind of seafood, so any pizza with any of that rubbish on is an instant no-no for me. Other than that, I'm cool with pretty much anything on a pizza. I particularly enjoy a meat feast, and I love me some jalapenos too on occasion!