My cats love basking on the warm bonnet of my car, and will stay on there even after I start it up. Once I reach a certain speed reversing out, they finally reluctantly jump down.

I do find little dusty pussy paw prints on it, but I haven't noticed any scratches. I think they keep their claws pretty well tucked in. My car wasn't in pristine condition when I got it anyway, so I haven't worried too much about that kind of thing. To be honest, I'm glad it isn't new - it's a big responsibility, trying to keep a new car looking new. Other things can mark your car if it's in the driveway - twigs falling off trees, neighbourhood kids throwing balls etc, people accidentally scraping the side as they walk past etc. Failing a garage (which I assume you don't have, or the car would already be in it), I'd go with a cover.