Credit cards are not swiped for any financial transaction, but may be photo or carbon copied to protect the owner in case you destroy something or decide to jet.
By using an unactivated travel credit card, you’ll have the plastic to show but won’t have to worry about a shady car rental employee from buying a Prada bag with your Visa. Just make sure to peel off the activation sticker before you hand it over.
This trick works just as well in the US, you can further protect yourself by claiming to be a EU citizen when booking through Orbitz and checking the global privacy rankings before your leave.