Occupations & Roles:
* Librarian
* Musician
* Magician
* Historian
* Technician
* Electrician
* Physician
* Politician
* Mathematician
* Comedian
* Guardian
* Parisian (someone from Paris)
Places & People:
* Italian
* American
* Canadian
* Australian
* Athenian (from Athens)
* Martian (from Mars)
* Olympian (from Mount Olympus)
* Asian
* African
Other:
* Avian (relating to birds)
* Martian (relating to Mars)
* Civilian
* Barbarian
* Pedestrian
* Vegetarian
* Olympian (relating to the Olympic Games)
* Terrifician (a word coined by H.P. Lovecraft, meaning "terrifying")
These are just a few examples. The suffix "-ian" can be used to create many different words, depending on the context.