Don't really have a clear cut favorite, but bacon is great with anything. On occasion when I replace pizza sauce with alfredo, chicken is my go-to topping.
I'm honestly more concerned that my pizza isn't dry, so I always order extra sauce. It never ceases to amaze me how much trouble places have with that concept- as if they don't put any on their regular order pizzas. I'd rather them screw up the toppings than not sauce it sufficiently.