Hellsing.

What's the result when the Nazis hiding in South America engineer an army of vampires and mount an all-out campaign of deathly dominance? Well, one thing you get is a little unity - seems the Protestant Hellsing Organization and the Catholic Iscariot agency might just have to think about teaming up. Looks like the First World War of the undead is about to erupt in history's biggest battle of blood and fangs.