Beers available by region of Bavaria:
Franconia - Landbier, kellerbier, Zwickl, Rotbier, Rotweisse, vollbier, Maibock, Dunkel, Rauchbier, Steinbier
Oberpfalz - Zoigl bier culture, and the above
Oberbayern - Helles bier, Hefe and dunkelweizen, Maibock, Doppelbock, Fest bier and Marzen, and Munich Dunkel. Leichtbier too I guess.
Swabia - Like Oberbayern but not as good
Niederbayern - Helles, and Saaz based Pilsner, Dampfbier and Roggenbier started here I believe.
Finding many of these beers even in other regions of Germany is very difficult, in some towns seemingly impossible (on tap anyway).
Nord Rhine Westphalia - saved by all the Altbier and Kolsch. Outside of Cologne and Dusseldorf their pubs will usually serve at least Alt, Kolsch, Wheatbeer and Pils which is a fair selection. Dortmunder lager appears in the Ruhr which can very wildly in quality.
Brandenburg - Gratzer, Lichtenhainer, Kottbusser (though you won't find much of it about in normal pubs, they are making a comeback)
Hesse, Rhineland-Palatinate, and Saarland - Shitpit of Bitburger and Krombacher. Apfelwein available.
Mecklenburg & Schleswig Holstein - Horribly gassy sharp joyless pils.
Niedersachsen - Rubbish pils mainly but greater variety of decent lager as you head south.
Saxony & Saxony Anhalt - Gose, Bockbier and Schwarzbier enliven things
Thuringia - Schwarzbier
Berlin - technically Berliner Weisse except you won't see anyone drinking it, however you will find loads of good Czech lagers for sale. A bad attempt at Pale Ale is commonly found too.
Baden Wurttemberg - Heavily reliant on and influenced by Bavaria.