Here's another quick game that you can play in the car, in a waiting room, or at a restaurant:
The first player names an object such as a fish, and everyone has to name a movie with a fish in it. (Finding Nemo or The Incredible Mr. Limpet would be good answers for this one.)
The player who names a movie first gets to choose the next object. You can also take turns naming movies that fit the category until you run out of movies.
This game also works with books and songs.