More into the seinen action stuff eh? Er, I think
Vagabond might be in your alley. I read a few chapters and it's pretty good, fantastic art, and lots of Beserk fans seemed to be into it. It's got the wandering warrior vibe in the samurai era. It well written, strong characterization and thought provoking with moments of brutality, and just in general well received.
Striving for enlightenment by way of the sword, Miyamoto Musashi is prepared to cut down anyone who stands in his way. Vagabond is an action-packed portrayal of the life and times of the quintessential warrior-philosopher—one of the most celebrated samurai of all time! Vagabond portrays a fictionalized account of Miyamoto Musashi's life, on a loose adaptation of Eiji Yoshikawa's novel "Musashi". Vagabond won the Grand Prize for manga at the 2000 Japan Media Arts Festival. The same year, Vagabond won the 24th Kodansha Manga Award in the general category. Vagabond also received the highly-acclaimed Tezuka Osamu Cultural Prize in 2002.
In the fucked up category, I'm going to mention but not recommend
Gantz. I can't recommend Gantz because it's the most fucked up thing I've ever read. Seriously it's gore porn and anything with boobs will be fetishized and at least almost be raped, and one of the few things mangas that made me sick to my stomach while reading. It's also quite over the top that it gets dumb.
Why say it? Because it's... weirdly fascinating. It keeps the reader off balance, has the intensity of Beserk and Claymore, and it just may be so fucked up that if it doesn't send you running, makes you O___o through more volumes. And it really gives no fucks about what it does.
I literally tried to find a manga page that was okay to show the action and I couldn't because they are all ridiculously nsfw. It's survival, gore, action, that's mission based and it involves a lot of bodies being exploded apart.
DO NOT watch any adaptation, stick to the manga.
If we are going into shounens, you might have already heard of them but:
Hunter x Hunter and Ippo are probably the two most revered mangas I've seen. You probably already read Hunter x Hunter in case you haven't seen the worship- but it's considered a "good" Naruto, it's written by the guy who wrote YuYuHakusho and because he's so damned good he's allowed to do whatever he likes. Seriously though you're not going to find many better action adventures, kind of a graduate manga when people leave the shounen three.
The fights are good, the arcs are creative, and I stopped reading after awhile because he had a sick break, but from what I heard it gets really dark.
The art is kind crap but that's because, as I said before, he's got so much sway he's allowed to do what he wants and he actually
refused assistants. That said, if it bothers you, the anime is suppose to be really good so if you want to watch rather than read there you go.
Ippo is a different flavor of shounen, it's about boxing. I haven't read it just because I've had so many people tell me to read it that I was doing it out of spite, but I did the same thing with Beserk.
It's pretty much
the ongoing shounen sports manga that doesn't rely on bishi boys, at least when it comes to critical fanfare. I don't know much about the anime and manga differences, but I've rarely met a group of fans who are more loyal to a manga, save for Beserk (and Beserk fans are the one that kept pestering me to read this).
I'm going to step away from your tastes to give some rather general other recommendations
Afterschool War Activities. This manga is pretty much the opposite of what you like, it's about Korea drafting highschoolers to help with the war effort against what they can only guess is aliens, and it's not a big adventure, there are no great heroes, and there's no insane action. It's a rather slow, character driven piece splayed around kids who actually act like teenagers but not in an anime/Dawson's Creek kind of way.
It
feels real, in the way they interact, in their pettiness, and in their eventual growth of devolution. Their focus is small, they don't do on a grand adventure and they don't get to see what the others are doing. It's just them in their small piece of the war, trying to deal with situations that often turn deadly.
It's not a long read, it's complete, but man the ending really knocked the wind out of me. The art is weird, but it's absolutely stylized and often is symbolic.
The next one is
20th Century Boys. Unlike the others on the list there's no action, there's no fighting.
And it is my favorite manga. Of all time. I consider it a work of art I'm not even fucking joking. I consider Urasawa Naoki nothing short of a genius. It's one of the best damned stories I read and I can't recommend it enough.
It's intrigue/mystery and has some of the best characterization I've ever seen, tight storyline, and brilliant plot twists. It's adults tapping into their inner childhood desire to be heroes, kind of, but it's more than that. I can't really explain it because I fear I'll give a lot a way, but it's a wonderful read. Please people, read this.
If you like anime instead, the same guy wrote Monster, which has a fantastic anime adaptation.
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I know there's more but it's been awhile since I hung out with the seinen/shounen manga people. I enjoyed a few mangas here but I'm too lazy to write them all so
Gangsta (its better than the name suggests),
Assassination Classroom (this is on my too read list, it's apparently really good and it's written by the same guy who wrote Nero, so it's a quirky mindfuck that doesn't devolve to much so that's it's too heavy to read), and
Liar Game- which is all about mind games and tricking people.
All good mangas.
