Responses
I suggest everything by Takahashi Tsutomu, especially Jiraishin and the Skyhigh series.
Also:
Himizu
Vagabond
Pluto
20th Century Boys
Akumetsu
Zetman
Vinland Saga
The Hour of the Mice
Shamo
Gantz
Eden
Historie
Berserk
Ubel Blatt
Monster
Basilisk
Battle Royale
Blade of the Immortal
Parasyte
and ill throw in CLAYMORE even tho' its shonen
Lookin for some dark seinen manga if anyone has any recs!!