I am probably Necro-posting, but this is a good series...
Title:Elemental Geleade, also called Elementar Gerad
Author:Azuma Mayumi
Genre:action, adventure, anime, comedy, fantasy, romance, shounen, supernatural
Status:Ongoing
Anime, Manga? Both! the manga is better in my opinion though...
Source:Elemental Geleade!!!
Summary:Coud is a young sky pirate who discovered a girl with mysterious powers on what had seemed like a routine mission. Ren (the girl) has the ability to lend Coud bizarre fighting capabilities, she, being part of a race of beings called Edel Raid, but being the possessor of a stone called the Elemental Geleade, she has powers even beyond the norm.
Other Works: there is one, but it has not been translated into english yet, and I cannot find any site to read it yet...