I have a serious addiction to Lic's Choco-cremes. They are so good - little balls of vanilla bean ice cream dipped in chocolate. Perfect for a special treat, and they keep great in your own freezer.
While those are my favorite, Lic's other goodies are great as well. From shakes to sundaes, I don't think you'll find a more classic "soda fountain" taste.
I usually visit for sweet stuff, but their deli choices are a nice change of pace from the average greasy fast food.