What is the name for paranormal investigators?

Answer 1

You said it! Paranormal Investigator is the most common. Ghost Hunters are less formal.

The group I head consider there to be a distinct difference between Paranormal Investigators and Ghost Hunters. Paranormal Investigators investigate all matters of the paranormal and try to work based off of some semblance of a scientific method. Doing field studies, and taking detailed notes and data to later be crunched into a report and sometimes scholarly papers to be written.

Ghost hunters are groups of people who get a thrill form finding ghosts..

But to clearly answer your question:

Paranormal Investigator, Paranormal Researcher, Psychic Detective (If the investigator claims to be psychic), Ghost Hunter, Parapsychologist (If the investigator has a degree in parapsychology).

Those would seem to be the most common.