Pin Pun is a classic Almagro pizzeria. Like all major pizzerias in Buenos Aires, the style of pizza is "al molde" which means thick crust, lots of cheese, and light on the sauce. You can order a slice or two to eat standing at the bar or sit at the tables in the back dining room to order a full pie.
I highly recommend also ordering a fried meat empanada or two, theirs are particularly great and you can see them being fried up right in the front window (tempting diners in from the sidewalk).