I don't know what part of what country you guys tend to be from, but up here in New England there's a pretty popular beverage company called Polar. They make a "draft style" root beer which has a slight bitterness that makes it one of the very best!
Oh, and if I wanted to spend like $3.00 on a 12oz bottle, I could sometimes go for "Rat Bastard" root beer, courtesy of Skeleteens USA.