Shaman King

7 words or less 

Using ghosts instead of pokemon to fight.

A few more words

A typical fighting-anime where everybody fights to be the best. The best at what? the best at being the equivalent of a necromancer: turning the dead into swords, spears, fireballs and you name it. To be fair it's not just dead people but an assortment of other spirits as well.

Like fairies and stuff

Character skills and abilities rise exponentially in a dragon-ball-esque fashion until what was once a glow around a weapon is now a giant fighting robot. Except it's not a robot but a spirit.

Forgetability 

At the time of writing it's been maybe seven or eight years since I've seen the series and I can proudly say that it's pretty forgettable. Some of the character design stays with you, much like our little aviator fairy above, but the same can't be said about the story or character development. 

World

This is the redeeming factor of the series. It's a world much like our regular modern-day boring world, but where people can merge with and harness the power of spirits, again, kind of like pokemon. It would make a great setting for a fighting game, maybe a rpg or two, and considering that not everybody can be a "shaman" and that their existence isn't widely known it could be easily blended into another setting. Maybe one with proper giant fighting robots.

TL;DR: Should I watch it?

Not really. - Unless you're researching special attacks