Avatar has many different and interesting classes to choose from. If you prefer the basic hack-n-slash variety, warriors or rogues may be for you. If you like magic-users, good choices are mages, clerics, and psions, while those in between can opt for the monk, a quick fighter and part-time spellcaster, as well as a very different style of play.
While all of the below classes are available at character creation, some of them will prove more difficult than others. The difficulty is marked with a '*'beside the name ( or '**' for very hard choices).