Was there any manga you read that messed with your head?

it could also be anime series too if you please that just turned your head in a ditzy whirl of confusion.And also why it messed with your head?

for me it was this one particular seinen manga i read many years ago that forever leaves a trace in my managa viewing days

http://www.mangafox.com/manga/watching_tv_all_the_time_makes_you_stupid/?no_warning=1

The reason being because how surreal and creepy it was the disturbing lack of optimism and camera angles.The submission to living and not caring about oneself at all in a spiraling downfall,yet so well presented is haunting.

Oh plenty have.
Elfen lied
Eden of the east
Gantz

edit
damn funny manga... his o face made me giggle.

Deadman Wonderland i had some music that went really well with it and its a mind freak by its self

Mirai Nikki. I was like whaaaaaaaa?

Holy Shit. I was just about to say this. But yeah, that manga messed with me. I was mind fucked.

Yeah me too. In fact, I'm reading chap 57 now.

Uzumaki was definitely a mindfuck.

Berserk. Ultimate betrayal of mindfuck.

Oh and the fucking carnival chapters along with tower arc (the chapters with the inquisitions). Kentaro Miura knows how to depict hell on Earth reeaaaaaalllllyy well.

Code Geass had me going WTF at a few Points,
Elfen Lied anime was somewhat "meh" especially the ending. But the Manga on the other pretty much mindfucked my head.
Higurashi gave me nightmares (no seriously, it did.)
Soul Eater and To Aru Kagaku no Railgun were both unusual at times, but not enough to be a complete mindfuck.

Oh yeah Seitokai Yakuindomo, why? because of how messed up the Student council is, (mainly speaking)

Definitely "Doubt" as well (the one were a bunch of people that were affiliated with a rabbit and wolf game get trapped and have to get out and find who's the killer among them, kind of reminded of "Saw")

It would be Parasite.

I read a manga titled "Nijigahara Photograph" or something close to that that confused the he'll out of me and had me scratching me head for days while I tried to figure out what the fuck happened.

NHK messed with my head a bit, although maybe for a different reason. I couldn't believe how realistic it was on a human level. There are a lot of stories that I've read that were entertaining because they had great plots or good twist, but welcome to the NHK showed that reality can be stranger than fiction - in a way at least. The desperation and depressing feelings shown were so strong that you though, "Okay, things have to start turning around - no way things can get any worst."

And yet they would get worst. Then you'd be shown a little sliver of hope for the characters, and then things would get even more depressing. The way it delves into the human psyche and what it takes to motivate a person who feels like they have nothing to live for was the most fantastic insight an Anime or Manga ever gave me into real human mechanics.