Saiyuki is one of my favorite mangas and has had a recent print rerelease by Kodansha. It's a take on the Journey to the West story, I definitely recommend it for dark fantasy. It looks like you can read a sample of the first chapter on the Kodansha site to see if you like it - (you need an account to see links)
ETA - oh lord and how could I forget. Pandora Hearts if you want some fantasy that is trippy and real grim. There was an anime release of it but it was comically low budget and barely gets into the story, I recommend the manga over it.