Gantz. This is probably one of my favorite Anime series of all time and certainly a classic, almost on par with Akira. I have not read the Manga but feel I should now, having watched all the episodes of the original Anime series in English dub from ADV Films.
*SPOILER ALERT* (discussion of plot elements to follow)
(above are Kishimoto, Kurono, and Kato, the three central characters of Gantz)
Gantz is probably one of the most ultra-violent Anime shows I have ever borne witness to, it completely oozes with over-the-top sexuality (and taut sexual tension)...and is cynical and darkly nihilistic. If you wanted to make an Anime series based on the mind and thoughts of Friedrich Nietzsche, it would probably come out looking something like Gantz.
This is Gantz:
...some weird alien sphere thing that serves as a weapons cache and also a preservation capsule for some weird alien that lives inside it. It occupies an empty apartment room in downtown Tokyo but is only ever accessed by the living dead, so to speak.
Gantz keeps a close eye on the lives of the citizens of Tokyo, and it chooses individuals who are on the brink of death and makes a kind of transporter "photocopy" of their entire chemical/physical make-up and transports them, fully conscious, to this strangely empty apartment room. It then taunts the new arrivals and explains their former lives are over and their new lives belong to it. It forces them to hunt down and kill other alien creatures living among the human population. It observes the battles like a Roman emperor enjoying watching gladitorial combat. It awards points to the combat survivors....and many do not survive. Those that die on Gantz's missions die for good and do not come back. Those that defy Gantz and try to leave the game before it is done also die horribly. Those that talk about Gantz outside the games also die horribly. Just like Fight Club, apparently you don't talk about Gantz either if you know what's good for you.
Gantz is sloppy, though, and sometimes produces copies of humans who end up not dying after all, like what happens to Kei Kishimoto, a young teen girl suicide who slit her wrists in the bathtub, but who was actually saved in the ER of a local hospital, but not before Gantz made a "copy" of her to play with in its sick games. The Gantz-generated Kishimoto has no place to stay and ends up staying for a time with Kei Kurono, the nominal protagonist of the story.
Kei Kurono, voiced by veteran ADV Films actor Chris Ayres (brother of Greg Ayers), is, admittedly, kind of a whiny, self-centered douche-bag at first, while his erstwhile childhood friend Kato is a more caring and generous soul. As they got older, the two grew apart and moved in different circles. When they first meet in Gantz's apartment, Kishimoto comes very close to being violently raped by a Yakuza thug, but Kato intervenes and saves her. Kurono is very attracted to Kishimoto himself but is a little dense when it comes to understanding and accepting why Kishimoto feels more affection towards Kato--who, oh yeah, saved her from being violently raped.
Kurono eventually finds his balls and becomes something of a bad-ass in Gantz's increasingly difficult missions. Kishimoto does notice and begins to feel respect and even some attraction for Kurono, but her heart still longs to be with Kato.
Every mission Gantz sends its "recruits" out on are deceptively "simple" and ALWAYS end up being more bloody and vastly more difficult that the characters are initially led to believe.
Kurono might have been able to win Kishimoto away from Kato had he played his cards more carefully and not been such a ginormous prick so much of the time, but alas, no. He does fantasize about her, though, and we do get to watch hentai-level explicitness for a brief interlude.
Still, one shouldn't feel too bad for Kurono, since he does eventually bang a super-hot late entry into the combat later on, and later tries to protect Monical Rial's sweet & fragile character who is a stalker victim murdered by her stalker in "real" life. By this stage of the story, Kurono is delusional and although we (the audience) see Monica's character as she is, Kurono sees Kishimoto in her place.
The ending is ambiguous, bleak, and nihilistic...bit of a letdown, I'll admit...but the series itself is so intense and so good, I really didn't mind the ending. It was adequate and it works. I'll have to look into how the Manga spins it later on.
Gantz was picked up and digitally remastered by FUNimation, who presented the first four episodes at a special screening at Alamo Drafthouse in Houston, Texas. I regret very much not going, having subsequently watched all the episodes on Netflix DVD, which owns the original ADV Films releases. I would seriously consider buying the box set from FUNimation, this Anime is that good. It is brutal, violent, with heavy sexual content and is not for the faint of heart, but it is also a brilliant work of Anime art and a true Anime classic.