My mom had an evil white cat. He would sit in the front yard quietly and wait for children. They would reach out to pet him then BAM he would hiss and scratch them.
I have a pure white cat, who's not evil, by any means. She is, however, the most neurotic creature I may have ever seen. Though, I do have her trained to come to my hand when I wiggle my fingers (she is deaf).
I used to watch a friend's cat that did this every time I entered the apartment when the owners were away. I always had to wear long pants because he would lunge across the room at me.