Catsbum

Anything by Junji Ito (there's a lot, I recommend Gyo and Uzumaki to start)
Dorohedoro (supernatural horror with wizards and a gritty style)
Grand Guignol Orchestra (zombies and a travelling orchestra)
Wolf Guy (modern day werewolf, gang violence, and highschool, VERY adult content including rape)
March Story (possessed items that take over people and kill others, artwork is eye candy)

Try this tag:
http://www.mangago.me/tag/horror/

Oops, forgot to put the links before I hit post. >.<
http://www.mangago.me/read-manga/uzumaki/
http://www.mangago.me/read-manga/gyo/
http://www.mangago.me/read-manga/dorohedoro/
http://www.mangago.me/read-manga/march_story/
http://www.mangago.me/read-manga/wolf_guy_ookami_no_monshou/
http://www.mangago.me/read-manga/ningyou_kyuutei_gakudan/

Also, here's a few more.
http://www.mangago.me/read-manga/black_paradox/
http://www.mangago.me/read-manga/litchi_hikari_club/
http://www.mangago.me/read-manga/drifting_classroom/

Enjoy! (= · u · =)/

i have read alot of horror... but am horrible at remembering names sorry .. ╮(￣▽￣)╭

rabbit boubt .
deadbrain
zero kage miko
judge

Yayyyyyy im so excited thank you so muchhhhh (づ￣ ³￣)づ

Thank youuu !! Ill try it (⌒▽⌒) !

Its okayy and thnk youuuu (づ￣ ³￣)づ

I'm yellow but still read some. Σ( ￣□￣||)
http://www.mangago.me/read-manga/haru_ni_kaeru/ Ch3 - 13th Moon magic
http://www.mangago.me/read-manga/nemureru_tsuki/
http://www.mangago.me/read-manga/teirui_makura/ Ch.2-3. Finger Biting
http://www.mangago.me/read-manga/to_the_sea/
http://www.mangago.me/read-manga/yokubou_no_shizuku/
http://www.mangago.me/read-manga/samenai_yume/

Omg >< thnk u so much ill read them ! Omo theyre yaoi /hurrayy/ hahaha

Adderall has a bunch of horror mangas. Try this list ----> http://www.mangago.me/home/mangalist/722/

Ah.. I'm not horror fan, I just saw this list..
Um.. His avatar matches with the list. Heh~(>‿O)v

This is a surprisingly interesing one. http://www.mangago.me/read-manga/shuuen_no_shiori/

Wait, I thought the avatar is Gin-chan. So, I didn't realize that it matches the horror list. I might be wrong. ╥﹏╥

here's my fluff list if you want to check it out:
http://www.mangago.me/home/mangalist/22515/

or try my type of seme list if you want more of that type of seme:
http://www.mangago.me/home/mangalist/26388/

http://www.mangago.me/home/mangalist/7551/
http://www.mangago.me/home/mangalist/7546/