As far as greasy pizza goes from squirrel hill, ivp has always been a secret major contender. They have had the $4 special (two HUGE slices with a drink) since I was a kid. Their crust is thin with a crunch and a perfect amount of cheese.
It is a small place with a row of small tables. It is a little on the dirty side and always has been. They are also one of the places that refused to hire women for a very long time, which annoyed me. But none of these things have been enough to steer me away from that special! Their take out pizza pies are also pretty cheap. They accept cash and card, unlike some of the other places around. One of my go-to places for a snack.