Yu yu Hakusho
Yu Yu Hakusho (which can be loosely translated into "the Ghost Files") is a manga and anime. and like most manga/anime, it all started with the manga.
Written by Yoshiro Togashi, it follows the life -- and afterlife -- of highschool delinquent, Yusuke Urimeshi. Yusuke starts out as a fight-picker and one-man-army at Sarayashiki High. While he usually spends his time in gang fights or gambling, he does occasionally go to school; but these rare occasions are often spent smoking on the roof or picking fights with local gangs. Hey, if it wasn't for Keiko -- a female student in his grade, and the victim of his skirt-flippings-- he wouldn't show up at all!
what i'm trying to say, is that Yusuke isn't the nice, selfless guy who'd sacrifice himself for some stupid little kid. At least, that's what the Underworld thought. Turns out, Yusuke did sacrifice his life for that stupid kid. You see, after getting in a fight with Kuwabara --a fellow student, rival, and soon to be best friend -- he was walking down the street when he saw this little munchin playing with his ball on the sidewalk. Apparently, this kid's mom never told him not to play near the streets, so when he accidently kicks his ball into the street.... well, what else is he going to do? what every little kid would! he runs into the street, and right in the direct line of fire from a speeding car!
So Yusuke, not thinking really, runs out into the street! he pushes the kid out of the way.... but ends up getting hit himself.
and thus ending his life.
yup. he died. but he was really supposed to. you see, the Underworld had no idea that he would do that! so they didn't erally prepare a place for him.... not in heaven or hell! When Boton -- the female guide to the Underworld -- tells him this, he's kinda confused. Boton then tells him that because of the fact that the Underworld is not prepared for him, they're willing to give his life back. If he can pass the test that is.
The test is simple. he's given an egg, and all he has to do is hatch it. this will happen by his just holding it. but what he isn't told, is that when the creature hatches, it will either be an angel or a demon. if it's an angel, good for him! pass go and collect 200 dollars! if it's a demon.... then he'll be devoured and it'll really annoying. to say the least.
While the first two volumes are kinda oneshot-ish and mystery oriented, the actual genre of the story would probably be fighting.
The actual story line and such doesn't really appear until the third volume, after he's been resurrected from the dead. This is when he begins his new career as an Underworld Detective.... that doesn't really solve mysteries so much as get into fights with a but-load if demons...
It's also in this volume that you get introduced to the rest of the cast: Kurama, a fox demon hiding in the human world; Hiei, a demon and rather.... indepent; and Kuwabara, Yusuke's fighting rival and probably his best friend.
I love this series, and would heavily recommend it! it also has an anime, and while i haven't really seen, i'm sure it's just as good! you can probably find it at your local bookstore in the Manga section.
so go check it out or something!
pictured above: Yusuke (front and center), Hiei (shorty with the black hair on the far left), kurama (pretty boy with the red hair in the upper right), Kuwabara (guy with the red hair and the glowy sword in the bottom right)