I've read so many vampire books and seen so many movies that I wanted to come up with a unique history and mythos for my vampires. I mention this because, as you know, the Nocent series revolves around a zombie vs vampire war. My zombies are unique too, but I'll talk more about them some other time.
The thing that makes my vampires unique is ectoplasm. Their flesh is infused with it. In my stories, ectoplasm is a substance that exists between the spiritual plane and the physical realm, as I mentioned in my blog about time travel. That is why conventional weapons do not harm vampires. Bullets pass straight through into the Other Side. Garlic nullifies the ectoplasmic properties and traps the vampire in our world where it becomes vulnerable to mortal weapons. Holy water has the opposite effect. It traps the vampire in the spiritual realm where it can no longer cross over into ours. Ectoplasm is also photo-sensitive and will dissolve in sunlight.
The last thing I came up with is that ectoplasm feeds off negative energy. Fear, anger and hatred will make a vampire stronger. Faith, hope and love can weaken it. I'll go into the history of my vampires some other time. I don't want to go too much into it before you've had a chance to read the stories which will illustrate it.