One or more electric bikes - We own two. Might not be as handy in some North American cities where car travel is imperative, but here in Europe, having a bicycle for getting around makes life so much easier. An electric bike is a lifesaver in hilly cities like Rome, where a motorino is too dangerous for a child to ride on and driving in the city center is impossible.
A Leap Frog Globe - Fantastic for learning geography or just minute facts about places near and far.
Friends who speak another language - Playdates with friends whose home language is not the same as yours will open your child's mind to the idea that his language is not the only one.
An open mind about new cuisines (and a closed mind to standard fast food) - This one is tough when your children are picky eaters. Last week, we introduced our daughter to Thai food. She wasn't too keen on it. The week before, she tried Indian, which she liked. We just keep presenting her with different kinds of food in the hope that one day, she won't always ask for pasta whereever we go in the world. :-) We never go to Macdonalds or Burger King, so she has never heard of those places. That way, there is no risk that she will want to eat there when we are on the road. :-)
Einstein Kids and Dora the Explorer DVDs - I'm not a huge fan of television but I have to give credit where it is due. These two programmes do a good job of introducing kids to other cultures. In fact, just last week, after watching an Einstein Kids episode about Igor Stravinsky's Firebird, our daughter said "Mommy, I would like to visit Russia. And I even have a snowsuit, so I wouldn't be too cold there.