Information on your approximate location would be helpful, there are many regional brands. Some personal favorites:
Berghoff (Chicago)
Rollie's (East Coast)
Sparky's (San Francisco)
This one might make a nice gift: Virgil's Special Edition Bavarian Nutmeg root beer. It tastes good, the nutmeg is noticable, and it comes in a nifty reclosable bottle. I admit I bought it for the bottle, but the beverage was good.
http://www.root-beer.info/brews/virgils_bavarian.php
As I mentioned in another thread, my personal favorite is Schell's 1919 root beer, but that is not available in bottles & cans.
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"It is better to have drunk and tossed
than never to have drunk at all."