Manga people may be interested in...
Shonen
666 Satan/O-Parts Hunter - By Naruto Author's twin brother. Pretty good. Anime? No.
Aflame Inferno - Recommended if you like Bleach. Anime? No. Korean Manhwa usually doesn't get anime.
Airgear - Written by Oh! Great (author of Tenjo Tenge). Great art, pretty girls, but mostly illogical and poorly written. Anime? Yes. Funimation youtube.
Akira - Classic Cyber Punk manga. Unlike the anime the manga makes sense. Anime? Of course.
Beelzebub - Action Comedy Shonen about a guy who becomes the babysitter of the demon lord. Fun. Anime? Yes.
Bio-Booster-Armor Guyver - Cult Classic Sci-Fi Action Manga. Anime? More than one, and 2 live action English movies.
Bleach - Sometimes Awesome. Anime. Yes.
Cage of Eden - Survival manga. Likeable characters, suspense. Anime? No.
Claymore - Girls with Swords. Decent plot tolerable characters. Quite violent. Anime? Yes. But stop watching after Rigald fight. Worst filler ending EVER.
Eyeshield 21 - Football(American Football) manga, with fun characters. Anime? Yes.
Fairytail - by Rave Master Author, it's like a badly written combo of One Piece and Naruto. Fun though. Anime? Yes.
Fist of the North Star - Shame on you if you've never heard of this. The grandfather of all fight manga. Anime? Yes. Many. Watch them all.
Full Metal Panic - Mech manga, with a bit of romance, and gag manga elements. Great villain. Anime? Yes, free to watch on Funimation's youtube channel.
Gamaran - Samurai's killing each other stylishly. Not too big on plot, but good action. Anime? No, but they'll probably have on in the future.
Galactic Legend of Warring State Heroes/Thunder Jet - Old school space Opera type manga with great characters and intrigue. Manga is hard to find in English. Anime? Yes, over 50 eps...
Hajime no Ippo - Great if you like memorable character great fights, and no ki crap. Anime? Yes.
Hikaru no Go - The writing and character develop is excellent. Even if you have no idea what Go is. Anime? Yes.
History's Strongest Disciple Kenichi - Usually Awesome. Anime? Yes. Free to watch on Funimation's youtube channel.
Hunter x Hunter -(by Yuyu Hakusho Author) - Great. Anime? Yes.
Inuyasha - Feudal Japan Action Drama Fantasy by Rumiko Takahashi. Anime. Yep, you saw it on Adult Swim.
Kyokai no Rinne - A modern gag manga with Inuyasha elements. By the same author. Anime? Not yet.
Medaka Box - Tenjo Tenge with more humor. Anime? Yes.
Mx0 - Highschool hijinks, humor, and magic. Anime? No.
Naruto - Usually Awesome. Anime? Yes, but beware of filler. Most filler out of any anime EVER
Nausicaa of the Valley of Wind. Awesome classic sci-fi fantasy manga. Anime? Yes an anime movie.
One Piece - Awesome. Anime? Yes.
Outlanders - Space Alien Girls with Swords written by Thunder Jet Author. Anime? Yes 1 OVA.
Prince of Tennis - Tennis manga. All around pretty good. Anime? Yes, but don't expect it to look like actual Tennis.
The Breaker - Recommended if You like Kenichi. Anime? Nope, Korean.
The Breaker New Waves - Same as above. Anime? Nope, Korean.
Veritas - Great manga. Anime? Nope, Korean.
Witch Hunter - Everything you expect out of a Shonen manhwa. Anime? Nope, Korean.
Shojo
Fushigi Yugi - Memorable characters. Last battle sucks ass. Anime? Yes. Good for a guy to watch with his girlfriend.
Jyu-Oh-Sei - Science fictiony Shojo. Anime? Yes. Free to watch on Funimation's channel. I only watched this because I was on a dating a chick who was into it. Fight scenes are too lackluster to hold the male attention span.
Vision of Escaflowne - Mishmash of Shounen and Shoujo,. Great character developement. Overall pretty good. Anime? Yes. And a crappy movie. In fact finding the manga is kinda hard.
...that's it. Don't watch a lot of Shoujo.
Seinen
Afro Samurai - Self explanatory. Yes this actually did start out as a manga. Anime? Yes, you probably already saw it on Spike.
Battle Angel Alita/Gunmm - Classic Cyber Punk manga, with great characters and action. Anime? Yes, and James Cameron is rumored to be doing a CG movie. Time will tell.
Basilisk - Ninja Action Suspense Drama with beautiful art and good story. Anime? Yes. Funimation's Channel.
Beck, Mongolian Chop Squad - Great story, great characters. Anime? Yes. Funimation Youtube.
Beserk - See Commander Guts brutally kill demons and anything else in his path. Anime? Yes.
Bio-Meat - Sci-Fi violence and suspense, and oddly no sex. Don't get too attached to anyone. Anime? No.
Black God - Fight manga about a guy who has a symbiotic connection with a demi-god fighter girl. Great action. No Black people. Anime? No.
Btoom - Gantz rip off. Still fun. Anime? No.
Dance in the Vampire Bund - Vampire werewolf stuff. Too much loli for me, but decent action. Anime? Yes, Funimation youtube.
Deadman Wonderland - Pretty interesting sci-fi esque manga. Anime? Yes. Free on Funimation's youtube channel.
Desert Punk - Post apocalyptic action manga, mostly humor. Anime? Yes, the dub is fantastic. Funimation youtube.
Devilman - Classic Horror manga by Go Nagai, spawned many rip offs inspired many RPGs. Anime? Yes, many and they are all intensely violent.
Dominion aka Dominion Tank Police - Written by guy who wrote Ghost in the Shell. Cyber Punk anime with lots of humor. Anime? Yes. Two. First one has excellent Dubbing.
Elfen Lied - Ultra Violent, Bizarre, and Depressing with elements of drama. Anime? Yes. Do not watch under the influence of alcohol or any other substance.
Freezing - Action Sci-Fi manga with huge breasts and violent fight scenes. Anime? Yes, but with much less plot and much more breasts. Funimation's youtube channel.
Gantz - Horror, Sci-Fi, Action, Sex, Violence, and Suspense. Try not to get attached to any character. Awesome read. Anime? Yes. But stop watching after episode 22, filler ending is unbearable.
Garouden - Fight manga. Senseless violence, and somewhat more compelling plot than Baki. Same author.
Anime? No, but the video games are pretty fun.
Genocyber. Cyber Punk Manga. Old school, very violent. Anime? Yes. Extremely violent. Only 1st OVA actually relates to the manga.
Ghost in the Shell - Edgy well written Cyber Punk Manga. Anime? Yes, more than one, all worth seeing.
Gunsmith Cats - Bounty Hunter girls with guns and explosives. Set in Chicago. Contains appearances by Bean Bandit one the greatest manga characters ever. Anime? Two if you count the one with Bean Bandit.
Grappler Baki - Fight manga. Senseless violence, memorable characters and incredible fight scenes. Anime? Yes.
Hellsing - Vampire Horror manga, with a badass main character. Anime? Yes, more than one. Second one is better than first.
Holyland - A great fight manga. Best damn ending of a manga I've read in a while. Anime? No, but a J-Drama exists and it ain't half bad.
Neon Genesis Evangelion. Sci Fi manga drama. Anime? Yes. Overrated, but still decent.
One Outs - Baseball manga with a psychological twist. Anime? Yes.
Shamo - Fight manga with an true anti-hero main character. Contains rape. Not for the faint of heart. Anime? lol, probably never.
Shigurui - only recommended for those who love samurai senseless violence with a homoerotic spin. Anime? Yes. Free to watch on Funimation's youtube channel. Violence looks even better animated.
Sun-Ken-Rock - Fight manga by Boichi. Beautiful art, good humor. Anime? No.
Tenjo Tenge - Fight manga. Great art, beautiful women, chaotic action, poorly written plot. Classic Oh! Great. Anime? Yes.
Ubel Blatt - Think Legend of Zelda with angst, darkness, sex, and violence. Great. Anime? Sadly no.
Wolfguy - Great artwork, action, memorable characters. Enjoyable if you can get over author's fascination with rape. Anime? No.
Y+M - Same author as Basilisk. More Ninja action drama, except more girls. Good plot. Anime? Not yet.
Zetman - A combination of power rangers and spider-man. Except very adult, and very grim. If you think your life sucks then read this. Anime? No.
Anime also on Funimation's youtube channel
Samurai Champloo
Trigun
Casshern Sins
Blue Gender
Darker than Black
Last Exile
Trinity Blood
Armitage III
FLCL
Devil May Cry
Heatguy J
Line barrels of Iron
Slayers
Initial D
Blackblood Brothers (Kinda like Hellsing except softer and girlier)
Full Metal Alchemist
Black Butler
I'll add more later.
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