For me, it's this, which is allegedly a pet repelling furniture cover.

It claims to be made of an aluminum-foil-like material, which will keep your cats and dogs off the couch. It might keep dogs off your furniture, and it'll certainly keep pesky humans off your furniture, but that kitty up there is a cat who is about ten seconds from turning that couch cover into a cat toy. I probably would've been more likely to buy it if it were stuffed with catnip and called a Cat Amusement Mat.