Mental Games

Here are a list of games that are mentally challenging.  They do not require a lot of physical exertion.  Most of these are great for indoors. 

You may find that games appear in more than one category. Where applicable I've cross-referenced similar games.

Camping Trip
Car Games
Car Games
Doggy Doggy
Four Corners
Heads Up Seven Up
Mother May I?
Ship Captain
Simon Says