NCTM: Principles and Standards for School Mathematics:

http://standards.nctm.org/document/eexamples/chap5/5.1/index.htm

This is a game played often in fifth grade when learning about equivalent fractions. You can play this game interactively online, too!

NCTM: Illuminations Principles and Standards : Number & Operations

http://Illuminations.nctm.org/imath/6-8/FactorGame/

The Factor Game engages students in a friendly contest in which winning strategies involve distinguishing between numbers with many factors and numbers with few factors. Students are then guided through an analysis of game strategies and introduced to the definitions of prime and composite numbers.