Dad's Rootbeer is Classic, although I like Stewart's Orange Creamsicle... reminds me of the fair in the summer...
Mountain Dew all the way, for as long as I can remember. I also love Mountain Dew Live Wire, but can't buy it many places where I live.
I don't generally drink the stuff. But remember thinking that Cream soda was cool when I was a kid. Or Iron Brew.