This term was first used in the 1960's in reference to the growing movement of radical, unconventional Christians who often displayed hippie leanings.
Tim "Hi, my name is Tim, and I'm Jewish."
Josh: "You need the love of Jesus in your life! Repent! You're going to hell!"
Tim: *walks away*
Josh: "Why do you hate me? Why must I be persecuted?!"
Person: "Well, have you actually seen Jesus or God?"
Jesus freak: "Um, no, but he talks to me in my dreams."
Person: "Uhh... yeah. Piss off, you creep."
1: proclaims the lord is coming with the imminent end of the world
2: has signs on their person, car, or home with bible quotes
3: goes to church more than once a week
4: started their own christian offshoot cult because the rest aren;t pious enough
5: tries to foist an extreme form of christianity off on others
6: is a born-again christian and/or fundamentalist
While these people aren't "Bad" people,they are usually intolerant to others religious beliefs. They tend to tell those of other religion that they are going to Hell and that they need to convert to Christianity. These can also be those who preach about their respective denominations. There is also a possibility that they could be homophobic.
Joe: No, sorry. I'm a very devout Jew.
Jane: *gasp* OMG! We must save your soul! You must convert, lest you go to Hell!
Joe: Oh man, your a Jesus freak!