Don't forget there's variation in there, usually of the introvert/extrovert flavor.
|Source: Columbia Pictures|
Egon Spangler is the token NT Rational: the nerd, the scientist. Always calculating, questioning, and over-thinking. Emotionally inept (unable to see the secretary's crush on him). Relies a lot on technology and is always inventing things.
These characters are typically nerds in movies, but keep in mind while there is truth to this, the most important thing is they are asking the big-picture questions and answering everyone else's questions with precision. They don't have to be scientists- they make great military strategists.
Ray Stantz is the NF Idealist: "The heart of the Ghostbusters." He is easily swept up in the ideas of others and has the enthusiasm and optimism that just makes you want to hug him.
Ray naively denied his divinity (after trying to reason with Gozer) and is the one who thought of the Stay-Puft Marshmallow Man because a happy, harmless childhood memory "just popped in there." While Idealists are known for being emotional, Ray shows they aren't totally wimpy either.
Peter Venkman is the quip-master SP Artisan. He sweet-talks Ray into a 3rd mortgage to pay for their business venture, and he has almost all the comebacks we love. Generally smooth under pressure (except when he was slimed) and lies like a carpet whenever he wants something.