Fuel & Fuddle is a bar & restaurant in Oakland - the heart of Pitt campus, but you'll find a lot of Carnegie Mellon students there, as well as students from other colleges. It's half off after 11 pm, so good luck finding a table.
I recommend their pizza - I get the flying buffalo often. I also recommend their nachos - plenty to share. Not anything to write home about, but still well made. Everything here is good.
They have a fairly big beer menu and drink menu.