Best pizza in Pittsburgh, period - try it if you have not yet. Then try it again with your friends to impress them all, claiming that it's some random pizza joint you found once.
The Pepperoni pizza is THE best.
The place looks like a dive bar in many ways, but the pizza could not be better. If you get take-out, bring a towel to put on the seat/floor of your car, underneath the pizza, as the grease will surely run through the cardboard and paper. And yes, the pizza is as greasy as it comes, so all you de-greasers (me included) will be in de-greasing heaven (or hell, depending on your viewpoint).