I'm still going with Red Ribbon as my choice.

Somebody had mentioned that most root beer is too sweet and heavy. Red Ribbon has higher carbonation, more flavor, and less syrup/sweetness to it. They also use real cane sugar instead of corn sweetners. It's hard to find, but a good choice.

Here's an article I found regarding Natrona Bottling (Makers of Red Ribbon Root Beer):

Natrona Bottling

There's a shop that sells mostly soda (including Red Ribbon and all of the Natrona Sodas for that matter) and other specialty beverages close to where I live in Los Angeles. It's a very interesting place to visit...sodas from all over the world, but only bottled drinks are sold here:

Galco's - Los Angeles