A wannabe Grammar Nazi who uses incorrect grammar but fails to see the error in his/her own typing, yet always criticizes others' grammar errors. They can be characterized by the idiom: Pot calling the kettle black.
A fake bitch on the Real Housewives of Beverly Hills. Has been accurately dubbed the "most hated housewife of all time" by Life&Style. She hates her Real Housewives co-star Kyle Richards, because Kyle called her out on being a bitch who's only famous because of her husband, Kelsey Grammer. She is friends with a fellow bitch named Alison who is supposedly psychic and who she invited to her dinner party so she could tell Kyle about how much Kyle's sex life sucks. She is about as real as Heidi Montag's boobs.
CamilleGrammer: That's who I am, Kyle!
Kyle Richards: No, that's who you're pretending to be.
A person who takes pains in online discussions to point out when someone has made a spelling or grammatical error. This is usually used as an ad hominem attack during an argument, as though spelling and grammar have a bearing on the validity of a statement.
While related to concepts like "grammar nazi", by contrast a "grammerfuck" is not just someone who is strict about spelling and grammar, but someone who actively uses this tactic to attack someone they disagree with, to avoid direct discussion, or to undermine a debate.
The spelling of "grammar" as "grammer" in the word is intentional, to demonstrate how much you don't give a fuck about their rhetorical attack.
Online Conversation:
"You're family is rich, so I think you've got a different perspective on poverty."
"I think you mean 'your'. Maybe you should ask for your college tuition back?"
"Hey, don't be a grammerfuck, how about making an actual point?"