I did a list for romance and one for battle manga. This list is just a compilation of various types of manga I feel are noteworthy. You may have read them; you may not have so given them a try. I understand that my explanations of most of these manga don't actually do the manga justice but I HATE spoilers and I HATE spoiling. So I'm trying to be as brief and spoiler free as possible.
#12 - Bastard - In a dystopian society, the Dark Schneider is revived in the body of a 14 year old. A dark fantasy, post apocalyptic seinen manga.
#11 - Oretama - The demon lord got sealed in the balls of the main protagonist. If he ejaculates, demons will destroy the world! A funny, mature ecchi manga.
#10 - Uzumaki - A small town in Japan is cursed by a spiral pattern. A short horror manga.
#9 - Tsubasa Reservoir Chronicles - The sequel to Cardcaptor Sakura. Li Syoran and crew must travel to the various worlds and dimensions in order to save Princess Sakura. Clamp.
#8 - Onani Master Kurosawa - About a perverted guy who likes to masturbate in the girls washroom. But he gets caught by a girl in his class and she starts blackmailing him.
#7 - Haikyuu - Volleyball sports manga about Karasuno, the fallen Crows trying to win it all. The main character is short but can jump really high.
#6 - Tower of God - If you reach the top of the tower your wish can be granted. 25th Baam enters the tower chasing after his only friend. A webtoon manhwa.
#5 - Kamisama no Iutoori (Ni) - A survival manga. One day a Daruma shows up in classes all over Japan to play Red Light, Green Light. If you mess up you die. This is a survival game where the main characters play a variety of twisted games and try to stop the mastermind behind it all.
#4 - Kiru no Iru Machi - It's a romance manga, but a good one, I don't really want to give much away. *review on it coming soon*
#3 - Area D - On an isolated prison island, there are beings with powers called "altered". This is a prison survival drama where the strong make it and the weak die.
#2 - Daiya no Ace - A very well written sports manga about Japanese high school baseball. Seido High School is trying to win nationals. http://www.blerdsonline.com/2015/06/grand-slam-of-sports-why-you-should.html
#1 - Blade of the Immortal - The tale of an immortal swordsmen who must slay one thousand evil men in order to regain his mortality.
Honorable Mention - 20th Century Boys - Another Urasawa Naoki masterpiece. A story about growing up and a world threatening conspiracy. A mystery drama, seinen manga.ki
Shoutout to -Umibe no Onnanoko - A short manga bout two emotionally damaged teenagers using each other for sex. But no strings attached is never as easy as it seems.