With my cats, it is more like what aren't they afraid of!
Two of them are scared of practically everything that makes noise. The vacuum, the washing machine, dryer, dishwasher, running water, etc. They're also afraid of the broom, and the outdoors. These two are also very afraid of strange/new people, and will hide for hours if someone they don't know comes over. Though I think the younger cat learned this behavior from the older. She's definitely the "boss" cat around here, and thinks she is a great big beast in a tiny little body, but it is kind of funny how many things she's scared of.
Our third cat is a bit calmer. She is afraid of some things, like the vacuum, but is also intensely curious about them. She'll follow me around the apartment while I vacuum, but she'll always watch from one room away. And she loves people, it doesn't matter who they are or how many times she's met them. In the whole time we've had her, she has never hesitated to greet a person at the door or sit on someone's lap. She's just a love.
