The shiny new car, topped with a big red bow and parked in the driveway on Christmas morning, isn't just commercial fantasy or every 15?-year-old's dream. Luxury auto dealerships in the Washington area say about 20 percent to 30 percent of their December sales are purchases made as holiday gifts, prompting them to keep a hefty supply of oversized red bows. About 20 percent of customers buying cars at the Rosenthal Jaguar in Vienna, Va., this month are buying holiday presents, sales manager Ogun Yilmazer said. The dealership is usually in on the plan, dropping the car off at friends'...