Exactly what I was going to say when I say the thread title. Even simple cheese pizzas can become really tasty just with mushroomadded on it. I also like sweetcorn.
Hmm. That's tough. There's loads of toppings I love, and my 3 fave pizza types are specialties that require a combination (Taco, Hawaiian, and Cheeseburger pizzas), but if I only got to have a single toping other than cheese... it would have to be... sausage.