Number 6
With Dr. Baltar and the Cylon, Number 6 (Any relation to 7 of 9?), I read that she has been hardcoded into his brain like you would load a program into a hard drive. He can sense her with all his senses, but nobody else can because she is only in his brain.
I do like this Baltar over the silly one in the origional show. He is a coward (Reminds me of Dr. Smith), but I don't think he hates the human race. He is just brainwashed by Number 6.