Billy Bat
Probably the best manga I've read in my life. It was so interesting.
Bloody Monday
Had an interesting premise but ended up a generic shounen title. Still had anime tiddies on one of the covers, which was great.
Death Note Oneshot
Describes the end of Death Note without any meaningful addition to the work itself.
Fullmetal Alchemist
Gantz
This is one of my favorites. Dark, twisted, sexy, and completely crude - just the way I like a seinen work. A long one, but def worth the read.
Holyland
I will never forget that summer. The summer when I first read this manga.
Akira