If you are in Japan and walk around the resident area, you will no doubt see a lot of large PET bottles lined along the pavement. These are mostly put up by older folks who believe doing so will keep away cats, either by scaring them with their own reflection in the water or the sunlight bouncing off the bottle.
Well, I am sceptic this works as I do think Cats are smarter than to fall for this. Below is a video to prove it. ^^;