I have been eating at Peppi's on the Northside for over twenty years and it never gets old. The only problem is sometimes they are so busy you have to wait a while, but I've learned to call ahead and pick it up.
My favorite is the Whiz - an extra large cheese steak with sauteed mushrooms on it. Their fresh cut fries are awesome (but eat them there - they don't travel as well as the frozen, processed fries from other restaurants). I also love the Italian Special which I have them add crushed cherry peppers to. It's also good hot, where they throw it on the grill for a minute or two to heat it up.
In the warmer months they have an outside patio in the back of the building which is pretty cool. It has an artsy vibe to it and it is a great place to relax on a sunny day.
Go there a few times and the owners, Jeff & Kim, and their staff will get to know you and make you feel welcome. Chuck always makes me feel at home and John always has something funny to share.
Be sure to feed the meter sufficiently before you feed yourself or your parking ticket might be the most expensive part of the trip to Peppi's!