Texas and Tennessee also use fleet plates (the TN plates have just recently started rolling out). California also uses a fleet sticker.

San Francisco has also somewhat recently passed a law requiring rental cars to be stripped of any markings that would identify them as rentals. The fleet sticker and small barcodes are deemed suitably subtle under the law.

When I rented from Hertz in St. Maarten, they rented vehicles with both Dutch and French plates. Running advice at the time was to take a car with French plates since the Dutch ones are marked as fleet and frequently targeted by thieves,