Don't ask where I came up with this list, I just did...
1. Claudia from Interview with a Vampire
2. Homer from Near Dark
3. David from Whisper
4. Eli from Let the Right One In
5. Laddie from Lost Boys
Bonus round... the Baby from Grace, Gregory Sackville-Bagg from The Little Vampire
Okay, let's deal with the bonus round first... the older brother in The Little Vampire, pre-teen/teenager who does the wrong things for the right reason. I thought the dude was creepy on the level that all 12-13 year olds are up to something.
The baby in the horror film Grace... babies are creepy by default. The idea that something is feeding off you, pooping and peeing inside of you... and then to find out once you give birth to it that it has fangs and needs to feed off of blood to survive...dude, the scene in that film when they show the mother breast feeding and you see all the sharp teeth marks/scars....nightmare inducing.
Laddie from Lost Boys is on this by default. The character has maybe ten minutes total in the movie, but it's a classic image of the kid under the bed trying not to vamp out while the Frog brothers are talking about him, and then he can't control it anymore and flies out from under the bed, ripping it to pieces in slow motion, clawing at the air...every babysitter's nightmare.
Eli from the original Swedish version of Let the Right One In, is disturbing on so many levels. Here you've got a centuries old vampire who decides to become best friends with a twelve year old boy, playing that come to me-no leave me alone- no come to me game of seduction, sets off my slayer's spidy-sense. As much as there is going on in this story, the surface of it is just disturbing.
David from Whisper. This is one of those films that might have gotten lost in the shuffle for a lot of people, but the idea of a child who can make you do things with mind control, and feeds off your emotions...double creep factor. I remember seeing this (and back to back with horror film Joshua both from 2007 about a little boy who is a psycho killer) and thinking that it was a brilliant take on the vampire genre. Not too mention, it's one of those films that has you wondering if what you saw was what you were suppose to?
Homer from Near Dark. Who could forget the old man in a child's body. It was one of the first films to bring up the topics of if you turn a child can they really fend for themselves as vampires? A trend that would be further explored in Lost Boys, Let the Right On In, and Interview with the Vampire...
Claudia from Interview with the Vampire... the original some would say (given the book was written in the 1970's) of vampire children. Here we are introduced to a character who is turned at such a young age, that they don't know how to be anything other then a hunter. As the character ages mentally, but stays trapped in the same body, we see her become more and more angry, till there is nothing left of her but despair. She's cruel, manipulative, and because of her resentment for being kept from growth, she becomes heartless. This was one of the first stories that dealt with the idea of the ethics of vampirism so bluntly. In fact, the one of the storylines is that ethics should always be brought into play, something Dracula never dealt with (there are more then a few scenes in Dracula where a baby is dinner) Her "evil" comes from a place of pain and confusion.
Okay, so I don't think anyone can argue that Claudia is the creepiest vampire kid ever. Wither it's the book or the movie, this vamp rips your heart out with icy-cold cruelty as much as with her fangs. The way the character underlines every single motion with the element of seductive manipulation, is played to perfection.