A non-exhaustive list of ways that one can get a familiar in Pathfinder, to give you ideas.

1. Wizard and witch get them by default.
2. Sorcerer can get bloodline familiars, which have an ability based on their bloodline.
3. There's a two feat chain that gives a familiar - good for combinations that are interesting but require a specific class, like ravenous tumbleweed/gunslinger.
4. Shaman gets a spirit familiar, which also has a special ability based on their spirit.
5. Tattooed sorcerer gets a special familiar which is inked on their skin when not active.
6. Magical child vigilante gets a familiar which they can transform into an improved familiar (an exception to the rule about not getting improved forms, since it's only available when the magical child is present and does not represent your character's natural form).
7. Calistria has a feat that grants a wasp familiar to devoted followers who do not have one.
8. Bard and rogue have archetypes that get familiars as either co-performers or accomplices in crime.
9. Alchemist can get a tumor familiar as a discovery.
10. Kineticist can get an elemental familiar as a wild talent tree.