Too many to list, but some of my all time favorites are pandora hearts, deadman wonderland and full metal alchemist. I also love pretty much every thing written by Junji Itou, even the weird stuff like the ones about ghosts who tickle you to death :3
One that I'm reading that I'm following is Kamisama Kiss. I just love it.
Another one I really enjoy is Kiss of the Rose Princess.

A few of my many favorites: Liar Game Death Note Skip Beat (still publishing) Aku no Hana (still reading) Ouran HSHC Pet Shop of Horrors BTOOOM! (still reading)
I read (I can't remember Japanese names) Black Butler Attack on Titan Yu-Gi-Oh!(the old one with Yugi)
There's a monster outside my room, can I have a glass of water?
Definitely Berserk. One of the darkest, most heart wrenching, and interesting pieces I've ever read, novels included.
Inubaka: Crazy For Dogs! Anyone heard of the series?
Hmm. So far Gintama. Then a tie between D. Gray-man, Hunter x Hunter, Akatsuki no Yona, and One Punch Man.
Way to many.
Skip Beat Barakamon One Piece OHSHC 3x3 Eyes (slatter³³³ :D) Bokurano Prince of Tennis Summer Wars Black Lagoon
Let me permanently delete my account instead of just "freezing" it.
Kaze to Ki no Uta, The Heart of Thomas and Rose of Versailles are my favorite manga. Someday I would love to be able to write stories as emotionally moving. Besides those I do like some less heavy stuff:
Poe no Ichizoku Gravitation Hellsing Ore Monogatari! Love Stage!!
and Oofuri because I love those baseball dorks.
I have to admit, my favorite right now? It's this really old one, done in the 70's, and translated when the US still flipped the books to the way English is normally read, rather than how nearly all manga is done now (retained in their original direction).
It's called Barefoot Gen. Written as a fictionalized version of the author's experiences, it follows a child, Gen, through his life in Japan. In WWII. In Hiroshima.
It's no spoiler to say it's about life before, during, and after the bomb. The first of the ten volumes ends on the day the bomb dropped, with the next few being "the immediate future." Following that, the series spans a longer period of time and into Gen's adulthood, how Hiroshima was effected in the long term by the US involvement, and the residual radiation.
It's a beatiful piece of literature, comparable to Maus on the level of "'comic' about serious topic from someone who was there" and absolutely moving.
But that's not what you're looking for, probably, lol. Personally, I love Madoka Magica, and most of the offshoot manga are pretty good (I'd avoid Oriko Magica, but it's a personal thing that I don't like about it).
Oops late, but definitely either Mushishi or Monster. I have personal faves I can't let go of (looking at you, DGM and HxH), but these two take the cake.
Skip Beat. It is an excellent read and is still ongoing. Excellent character development and awesome heroine.
i can read Fullmetal Alchemist forever. * u* although i never did finish it...
i also love Nana by Ai Yazawa - i'm still really upset that it's on an indefinite hiatus.
My all time favorite Manga that I have ever read still to this day is, Saiyuki, its not one of the more well known ones [at least from what I have gathered.] Its an older series that isn't in production anymore, but its full of gods/goddess, demons, half demons, dragons, priests and so much more. Its got a great story in the heart of it all and the art is just to die for!. [Never watch the anime though its complete and utter trash DX]
For me, it's probably a toss up between Saiyuki and Yu Yu Hakusho. I have to say both, because there's no way I could choose.
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