I feel like not enough people have given feta a try. Maybe because it's usually a premium topping and you have to pay a little extra for it, or maybe because it just looks gross. I usually only get it when I'm stealing food from work. But damn does grilled chicken, feta, tomato, and onion make a tasty pie.
In my neck of the woods there are nearly as many pizzerias as there are Dunkin Donuts, so there's an arms race for which place makes the best specialty pies.
S-tier:
Taco pizza where the only thing you see from above is a bed of shredded lettuce
Baked Ziti
Chicken Bacon Ranch
Chicken Parm
Cheesesteak pizza where the pizza is over an inch thick entombed under an additional top layer of bread
Honorable mentions:
Mashed potato and bacon
Macaroni and cheese
BBQ chicken
As far as normal toppings go, sausage and green peppers is pretty solid.
:gulag:
Agree that baked ziti pizza is S-tier
CARBS