General:
* Individual
* Human being
* Human
* Soul
* Being
* Creature
* Entity
* Body (more formal)
Formal:
* Individual
* Subject
* Citizen
* Resident
Informal:
* Guy (male)
* Girl (female)
* Dude (informal, male)
* Chick (informal, female)
* Fellow
* Folks (plural)
Literary:
* Mortal
* Wight
* Being
* Creature
The best synonym for "person" will depend on the specific context in which you are using it. For example, if you are writing a formal document, you might choose "individual" or "subject." If you are writing a casual conversation, you might choose "guy," "girl," or "dude."