In case the dollar or euro fails during your flight home, you can always shore up your assets by picking up a few gold bars at a Gold to Go vending machine, debuting in the above airports in May 2010 after a successful 2009 test run at Frankfurt. You can also buy South African Krugerrands, Canadian maple-leaf coins, or even a $100, one-ounce Australian Kangaroo coin.
Price: They fluctuate, supposedly pegged to real-time prices. We were quoted $50 for a one-gram gold bar, complete with fancy gift box. Turns out you could do a little better, price-wise, on eBay, but as airport gifts go, a gold bar still beats another dumb T-shirt.