I'm from Harrisburg, PA. Some of the best things are:
Shoo-Fly Pie. Seriously it is a combination of complete and utter molasses bliss than you will fall in love with and want to marry.
Middlewarths BBQ Chips & UTZ chips
Also, and I didn't realize that this did not happen outside of the East Coast, but Made To Order food at gas stations. We have a wonderful gas station called Sheetz(which is almost as good as WaWa) that serves MTO food. You can order specialty drinks, pizza, burgers, sandwiches, paninis, salads, soups, wraps, ANYTHING made to order at your local gas station and it'll be ready in less than 5 minutes. So I will add Sheetz to the wonderful list of local food even though it serves everything you ever wanted.