Paris France Optional +
Some other suggestions, although not necessary - Travel pillow, chewing gum (especially for those who have ear problems during flight), book and/or ipod and one change of clothing (air lines do lose luggage occasionally)
For a great view of the city (especially at night) go to the top of the Eiffel Tower at Paris. It also offers a great vantage point for viewing the water show at the Bellagio.
If you have a high-def video camera, be sure to take it on a hike with you to the bottom of the canyon. HD is the only way to bring out the gorgeous contrast of blue sky and red rock that you'll want to show everyone at home.