CLAYMORE!
Well I'm reading the books and seen the anime so I pretty much love it.
The anime covers 10.5 of the books and then drifts off and ends, but overall the anime is great, but the manga's better =P
Guessing you don't know anything/much about it soooo..
The story is about a "Claymore" called Clare, A boy called Raki and Creatues called "Yoma".
Clare is a "Claymore" that's half Yoma and Half Human with super strength and a giant claymore (sword) and her job is to kill Yoma for the organisation that creates and controls all the claymores.
(small spoiler) At the start she meets Raki who is interested in her from the start and after that he's pretty much addicted to being by her and being able to fight with her and protect her.
After a while into both the anime and manga it covers the reasons why Clare's a claymore and why she trys to hard..
Overall it's pretty action filled with a good storyline