The best travel games are those that don't require any special equipment -- or take up any extra room in a backpack or the backseat. And the truly great games are ones your kids will want to play again and again. These games can become a tradition that your children may introduce to their own offspring someday.
In your travel tradition arsenal, keep games like "I Spy." Take turns letting each child spy, with his "little eye," an object or color inside or outside of the car or airplane as other family members try to guess what it is.
On a road trip, try to find a license plate from each state, or give it a twist for older kids: Turn license plate letters into acronyms. The letters ILC, for example, could mean "I like carrots" [source: FamilyFun].