When people fuck up mental disorders (MPD, Schizophrenia, PTSD, etc.) It pisses me off because I'm studying to be a psychiatrist.

There was one Harry Potter fanfic I read where the author not only had no knowledge of the series in general before writing the fanfic, but also shoved his religious views (Christianity) down all the readers' throats.

This is why Christians (me included) are getting a terrible reputation. Because there are some authors who do try to shove their religious, political or ideological views down your throat every F***ING chance they get. Case in point, the late IKillFaguts.

People who write period pieces (especally WW2 period pieces) who don't seem to know anything about the time ther writing about,except what they heard in history class.

I hate when they get a canon wrong solely out of ignorance and in order to boost up their OC in saying "yeah they knew a lot about that" even though they obviously didnt.

I read a Teen Titan fic a few weeks back where the OC looked at Gizmo's technology and said it was total junk, that the tech salesman sold him a downgrade. I commented and asked her if she was going to walk up to Robin, a guy raised in the circus, and tell him how to do a better backflip. Gizmo makes his own equipment, he doesnt buy it, and it's some of the best gear (at least that's more or less how they have him written in canon).
She confessed that she didnt know much about Gizmo and just wrote it that way. I noticed that she does that a lot, but it's also something that many suethors do...
"I dont know anything about this but I want to inflate my OC anyway, sooooo..."

I hate doing that, personally. When I'm writing I hate not knowing something that is happening. If my OC doesnt know what's going on, that's fine, if its not in their profile that they're educated in the field. But I'd rather research something before I write anything about it. Even one scene. One two-minute scene can take me a week of research, but it's well worth it. And if someone comes along to tell me "hey, you got this wrong" it's usually someone who misread what I wrote but when they really are right I love being corrected. My ego doesnt, but I dont listen to him ^_^

OK last one, Anti-social is not what you think it is, in other words... Look up Charles Manson.

Ugh! People pretty much already said all of mine but I might as well throw in my two cents.

Molestation/trama: I have a friend with a major sue who tried writing something like this. I had to take two steps from my computer and beat the shit out of my pillow before I put my fist through my screen in an attempt to get at her! She treated it as... well like a pity card and I knew someone molested by a family member [this also ties into cutting] she was a sweet girl but she would get weird and act out [violent mood swings and just overall odd and unusual behavior], she started cutting and in a way... it was a good thing because that brought attention to her and it helped her get out of the situation. I get so mad when people abuse or use any form of trama as a pity card or those who use cutting as a "they feel sad! They're just expressing themselves!"

Mental illness abuse: Stop it! Fucking stop it! Seriously you think schizophrenic is so silly and hard core or some shit? Seriously have you ever met a person who will be normal one second and then just... zone out, repeat what they were saying in a strange loop or just start screaming at something you don't see? It may sound funny to most but it's darn right scary! And paranoia or OCD I have that shit and God does it burn me up when people make it sound like they are just a bunch of neat freaks! You try staying up for 5 hours in a dead panic! And I read a few people mention MPD or as it is now called DID. I have a character with that disorder and yes I've done all the research, I did not stick to one source, I found many, I've watched Dr.Phil [guilty pleasure I admit] and talked to my psychiatrist! It is not all, "they get scurred and they turn into a bad persons! But it's ok even if they don't do anything bad it's not really them!" It's not a get out of jail free card! Also I had some one say this to me once, just because a character is diagnosed with one disorder it doesn't mean there aren't others! Example: DID has the following, depression, PTSD, eating disorders, sleep disorders, amnesia, anxiety, compulsive behavior and in some cases Auditory hallucinations, and very rarely visual hallucinations. And because of the changing of "alters" it often seems like the person is going through mood swings. So take all that in, the person would have to be studied for quite a while to come up with a proper diagnosis and in most cases it is misdiagnosed as schizophrenia. Now to cutting, I get tired of cutter characters too, mainly about how they are portrayed, seriously DO SOME RESEARCH! [God sometimes I get so tired of saying that...] Ok ok, enough on this section for now...

Misrepresentation of cultures: RESEARCH! I might as well just say that for everything now... but anyway, the only way you can really get away with somewhat getting a culture wrong is if you're creating a culture based off of an existing one.

Ok I'm done for now, or this message is going to go one FOREVER! TTMTT