It's... the Stay-Puft Marshmallow Man.

Ghostbusters is so chauvinistic! Oh – My – Gosh!

Quotes from the movie, compliments of IMDB.com:

Dr. Peter Venkman: All right! This chick is TOAST!
Dr. Peter Venkman: [as the Ghostbusters approach Gozer] Grab your stick!
[the Ghostbusters draw their handsets]
Dr Ray Stantz, Dr. Egon Spengler, Winston Zeddemore: HOLDING IT!
Dr. Peter Venkman: Heat 'em up!
[they arm their packs]
Dr Ray Stantz, Dr. Egon Spengler, Winston Zeddemore: SMOKIN'!
Dr. Peter Venkman: Bang 'em hard!
[they rack their handsets]
Dr Ray Stantz, Dr. Egon Spengler, Winston Zeddemore: READY!
Dr. Peter Venkman: Let's show this prehistoric bitch how we do things downtown... THROW IT!
-----
Casey Kasem: Still making headlines all across the country, the Ghostbusters are at it again. This time, at the fashionable dance club, "The Rose." The boys in gray slugged it out with a pretty pesky poltergeist, then stayed on to dance the night away with some of the lovely ladies who witnessed the disturbance.
-----
Dr. Peter Venkman: Nimble little minx, in't she?
-----
Dr Ray Stantz: Your girlfriend lives in the corner penthouse... of Spook Central.
Dr. Peter Venkman: She's not my girlfriend. I find her interesting because she's a client and because she sleeps above her covers... *four feet* above her covers. She barks, she drools, she claws!
-----
[Dana is possessed]
Dr. Peter Venkman: I make it a rule never to get involved with possessed people.
[Dana starts passionately making out with him]
Dr. Peter Venkman: Actually, it's more of a guideline than a rule...
-----
Dr. Peter Venkman: I'll take Miss Barret back to her apartment and check her out.
[Dana Barret looks up confused]
Dr. Peter Venkman: I'll go check out Miss Barret's apartment. OK?
-----
Dr. Peter Venkman: Type something, will you? We're paying for this stuff! And don't stare at me, you got the bug-eyes.
[pause]
Dr. Peter Venkman: Janine, sorry about the bug-eyes thing. I'll be in my office.
-----
Dr. Peter Venkman: Alice, I'm going to ask you a couple of standard questions, okay? Have you or any of your family been diagnosed schizophrenic? Mentally incompetant?
Librarian Alice: My uncle thought he was Saint Jerome.
Dr. Peter Venkman: I'd call that a big yes. Uh, are you habitually using drugs? Stimulants? Alcohol?
Librarian Alice: No.
Dr. Peter Venkman: No, no. Just asking. Are you, Alice, menstruating right now?
Library Administrator: What's has that got to do with it?
Dr. Peter Venkman: Back off, man. I'm a scientist.

Seems to me like our hero, the charming, funny Dr. Peter Venkman (Bill Murray), is a PIG!
The woman he is chasing (his client!) is Dana Barrett (Sigourney Weaver). She is possessed by Zuul, the minion of Gozer. Gozer is trying to bring about the destruction of the world. In the final encounter between good and evil, between the Ghostbusters and Gozer, Gozer “chooses” to take the form of a woman (actually, this is the writers choice). To boot, the woman form of Gozer has a short, male haircut, as if she couldn’t bring down the world looking like Marilyn Monroe. This is before she becomes the 400-foot Stay-Puft Marshmallow MAN. Obviously Gozer wasn’t able to get it done as a woman. The day is saved when the Ghostbusters (four men) “cross the streams,” the ultimate combination of futuristic falic symbols. And of course, Peter Venkman, the arrogant, funny, chauvinistic bastard he is, who has been pursuant of Dana throughout the entire movie, who in the first scene we see him is rigging a “test” for telepathic powers so that he can impress a cute blonde, who, of course, is dumb enough to fall for it, and agrees to let Doctor Venkman take her out on a date, who is obviously not as good a doctor or as smart as Ray Stantz (Dan Aykroyd) or Egon Spengler (Harold Ramis), is undoubtedly depicted as the leader of the Ghostbusters and the ultimate hero. The world is saved and Venkman gets the girl. The male fantasy realized.

More quotes just because I love this freakin’ movie:

Dean Yeager: Doctor... Venkman. The purpose of science is to serve mankind. You seem to regard science as some kind of dodge... or hustle. Your theories are the worst kind of popular tripe, your methods are sloppy, and your conclusions are highly questionable! You are a poor scientist, Dr. Venkman!
Dr. Peter Venkman: I see.
-----
Dr Ray Stantz: Everything was fine with our system until the power grid was shut off by dickless here.
Walter Peck: They caused an explosion!
Mayor: Is this true?
Dr. Peter Venkman: Yes it's true.
[pause]
Dr. Peter Venkman: This man has no dick.