An ID card and question ref Military Discount got me a Ford Mondeo upgraded to a Lincoln Town car (Same car the President uses) without additional charge. Petrol for pennies and a motor like that added a lot to the holiday.
The 'tipping culture' of the US managed to bug me. My philosophy is 'Good Service = good tip. Their culture is 'Any service = tip' which wasnt compatable with my '!!!!e service from a grumpy old cow - sling your hook' attitude.
http://www.militaryspot.com/military-discounts.htm
May help - unverified