If you liked the Soul Eater manga, the Anime-Planet community thinks you'd like:
Both Soul Eater and Rust Blaster play with the idea of people being able to turn in to weapons. With Rust Blaster, transformation is a little different, though. But if you like fight scenes like that, then one manga is just as interesting as the other. Rust Blaster and Soul Eater also have the theme of not losing yourself, of fighting forces out of the character’s control and staying true to themselves. Although Soul Eater doesn’t have vampires in it, and Rust Blaster does, I think if you like one, you should give the other one a read. If Rust Blaster lovers are looking for something longer to read, check out Soul Eater. If Soul Eater lovers are looking for a something short and sweet, try Rust Blaster.