CHORF is an acronym coined by Brad R. Torgersen to describe the worst sort of fans. The term actually stands for Cliquish, Holier-than-thou, Obnoxious, Reactionary, Fanatics. Unlike terms such as SMOF there is no good side to being labeled with this term.
A person who is a CHORF is specifically trying to prevent others from enjoying the topic that they profess to enjoy. Their group of friends and accepted acquaintances/allies are the only true fans. They often administer 'tests' that are designed to force someone to prove that they're a real fan (think of the kid who confronts you at a comic convention demanding that you answer them when they ask, "What happened in issue 12 of Green Lantern, volume 1, page 7, panel 4?"). They express a superiority over others for their self-perceived superior knowledge on the subject. When confronted by any change or imagined threat to their favorite subject they react with volatility (think of the kids who drop rape and death threats because you suggested that maybe a comic book cover shouldn't pose the women in sexually suggestive ways when it's specifically targeted at little girls).
A CHORF is a complete jerk and is unwelcome anywhere they go.