Nearly all of my creatures share a single vulnerability. Head trauma. A serious blow to the head can wobble a vampire or even a lycanthrope. Because, even with a vampire’s ability to repurpose cells on the fly, the one part of the body that isn’t affected by it is the brain. Because it’s only in the fact that the brain remains human that allows THEM to remain human rather than a colony creature pretending to be human. You manage to put a bullet in a vampire’s eye, s/he’s history. They’re really fast, so this is not nearly as easy as it sounds. And if you miss, you probably won’t get another chance.
Lycanthropes are just solid. Their muscles and bones have increased tenfold in sheer density. Weres easily shrug off small arms fire and heal any minor injury nearly as fast as a vampire.
Hit a werewolf in the head with a big enough sledgehammer, though, and that super-dense skull isn’t going to be much help. The brain has no such protection.
Of course, getting close enough to HIT the were with the sledgehammer is another matter entirely.
I got into an argument with a fellow some time back about which was harder to write–SF or Fantasy. It was his supposition that SF was harder to write because it had to be “real.”
Creating a consistent fantasy world, on the other hand, requires a LOT more creativity and, in reality, conscientiousness. It’s very easy to justify changing the rules just to further a plot point, and the only one you answer to is yourself. At least in the short run.
For example, say you’re working in pure SF. If something goes wrong, you can’t change the laws of physics to make something work. If you’re writing fantasy, you CAN change the laws of magic, say. But to do so will undercut the illusion of reality you created and cost you in the end. If you do not keep consistent rules in your universe, your universe is little more than a realm of wish fulfilment.
Now it’s possible to ADD to those rules, to create new situations that incorporate the ideas of the old rules but expand them them.
My magic system is like that. The two requirements to use magic effectively (beyond the first, which is simply having the genetic coding to work magic) are creativity (imagination) and knowledge. You have to understand something to manipulate it with magic. Which is why there are specializations like mage-engineers and mage-physicians. These are people who, through study, have learned to apply magic to physical laws and biological systems.
A mage-physician, or anyone who’s been taught the trick, can use his or her knowledge to knock someone unconscious by a simple blast of energy to a specific region of the brain. Someone who doesn’t know the trick, on the other hand, might do ANYTHING in making the attempt.