Two of my cats are afraid of my sewing machine. I don't use it as often as I'd like, but when I do they run out of the room and peek around the corner to see what on earth the silly human might be doing. It's really funny. I have to admit that sometimes I stop and start more than I need to just to see their little black-and-white faces with the terribly confused expressions.
All of my cats are terrified of the vacuum cleaner. I just have to put my hand on the handle and tails become brushes. Rapidly disappearing brushes, for that matter. They don't peek around the corner for this one. In fact, the 18-pounder, Moon, usually tries to hide behind the toilet. River and Kaylee retreat under beds and bookshelves.
My cats aren't afraid of the squirt bottle. They are resigned to it. When I put a hand on it, they usually stop whatever they're doing - but they do it with an "oh, no, not again" face. No puffed tails, ears stay upright.