This one feels surprisingly forgotten, let's fix that.

Yoh Asakura is a Shaman, someone who can communicate with spirits, but as fate would have it, Yoh is destined to fight for the right to be Shaman King against his evil twin Hao, joined by his spirit ally Amidamaru, best friend Manta, fiancee Anna and a host of allies, rivals and former enemies, Yoh sets out to defeat his brother although his laid back nature doesn't always leave that impression.
For a time, this was easily the most unique among Shonen Jump's properties, with Yu Yu Hakusho finished and Bleach still finding it's stride, it filled a void for a couple of years.
It's memorable for a couple reasons, it took alot more risks with it's content using some quite brutal scenes, particularly in the manga; it's host of characters felt unique and colourful, the action was colossal and it's ending really came out of left field.
It's biggest issues seem to stem from being dragged into Shonen tropes which ultimately made the anime finish on a cheesy power of love and friendship ending not helped by 4kids dubbing which comes to another baffling decision as to why 4kids of all companies picked up Shaman King in the first place; keep in mind just Faust VIII alone cut open Manta's chest cavity and in the same battle drugged up on pain killers cuts open his own leg, rips out his leg bone and asks for a replacement, before Joco even became a hero, he was a violent gang leader who murdered in cold blood, in fact listing all the deaths in the show would make Light Yagami blush, although it does make the 4kids dub hilarious at times especially when they forgot to censor blood in a couple of scenes and don't get me started on HoroHoro.
I didn't mind the dub too much but some of 4kids choices were atrocious.
Ultimately what killed the franchise was the fear of being written off as another wannabe Shonen Jump title competing for scraps left by the big three with only a handful allowed to sit with them. This is probably why the creator pulled the plug before the finale and has spent the last 15 years piecing together the finale and epilogue.
Final Verdict: An original Shonen title among a sea of regulars in it's day, let down by how it's anime ended and who it was dubbed by, ultimately leaving it's actual ending to be released long after the franchise ceased production.