I guess favorites would be
Dad's Root Beer
A&W Caramel Cream Soda (which I haven't actually seen in a store in a decade)
When I went down to Ohio on a road trip a few years ago I noticed that brands that we get here actually tasted different. It was like buying soda fountain drinks made with chlorinated tapwater, but they tasted like that right out of the can.
I wonder how much impact the local bottling/canning companies have on what is the most popular drink in a given area.