9. Elements Letters
Sheldon attempts to play this car game with Penny, but ends up playing by himself, in "The Euclid Alternative" (Season 2, Episode 5).
How To Play:
One player begins by saying an element, then the other player says an element where the first letter starts with the last one that the first player said.
For example, player one says "helium," which ends in "m" and means the next player could say "mercury." That would mean player one would have to come up with an element beginning in "y," and so on.