Italy was it for me. The train station in Rome was crazy. And just Venice in general. I was probably just in the touristy areas, but it was definitely the most hardcore non-stop street scamming I'd been around.
I was told later by a guide that if you say “no, grazie” in a semi-convincing Italian, they’d assume you’re local and leave you alone.
That's weird because in Venice I never had a single problem, didn't feel scammed or anything, ate in very nice restaurants (I do avoid the tourist shops and restaurants though) and the people in general were nice. I almost felt at home, and many shopkeepers even spoke French, maybe better than English (I am French). I don't think anybody in the street accosted me at all, anyway. I'd go back without any hesitation.
Never had a problem in Italy with a +20y old junker car even with swiss plates.