Currently at the top of my list of favorite Manga, Claymore is a wonderful story about an nameless organization who tracks down and kills monsters, called Yoma, who prey on normal humans. Shonen Jump readers may remember the preview for it quite a while back. It has exceptionally awesome action sequences, along with a deep storyline involving the use of power, and consequences that come with it.

They've only released up to number three over here, I believe, and the story shifts in the third one to another character, though I suspect it's more of a flashback than an actual full shift in the story. I do like how the current storyline shows that though Clare is cold to most people, some of the Claymores can be alot more so.