In this country a Fiat Cinquecento Arbarth, rented solely to compete in at an auto test, it was an absolute hoot, it went back with four bald tyres and a broken speedo, they said nothing and didn't charge for the defects.
In the US it has to be when I ordered an Escort sized hatchback, walked out to the Avis lot and there in the space they sent me too was a V8 Grand Cherokee, kind of cool when I was that young.