The Higurashi and Umineko manga are pretty good adaptations of the sound novels. I used to read them years back but the translation releases were confusing so I thought I'd wait a bit. I really have to check them out again some time.
Whenever I start reading manga, I can't seem to finish them. I've read Monster, As the Gods Will (a bunch of students in a death game), and Uzumaki (a town where everyone gets obsessed with spirals). Uzumaki disgusted me so much I'm not sure if I'd go on reading it.
I tried Pupa It's about a regenerating guy and his sister who turns into a cannibal. She eats him of course (no reason I should be reading this if not) and got quite far until I realized how shitty it actually was and stopped.
KissxSis for something lighter and something ecchi. There's also Momoiro Heaven which could be really amusing. The heroine writes erotica and they're so funny to read. There's also Midnight Secretary, whose heroine I like.
Aku no Hana is pretty intense. The latter half of the manga felt like I was reading an entirely different story. Overall, it was a touching coming-of-age read. One of the few manga I actually finished.
I read the Shuuen no Shiori manga too. It's originally a vocaloid series about four friends who got themselves in a death game where they must kill the 'fox,' which is one of them. There's something really interesting about highschool students killing each other, I don't know. Maybe I'm just a heartless person.
Shingeki no Kyoijin. Since I couldn't wait for the second season any longer.
Recently, I'm reading Parasyte and Gyo. Gyo is weird but Junji Ito's works are kinda weird in general. Gyo has fishes with legs. Said fishes terrorize people. I haven't seen anything this weirdly terrifying since Stephen King.