Pendulums are divination tools, used to answer yes/no questions to assist in providing direction.  They work by responding to your subconscious mind.
 
Sodalite
Associated with 3rd Eye Chakra
Sodalite is used to unite logic and intuition, eliminating mental confusion.  This stone is great for gaining clarity on questions when you feel you may need additional clarity/objectivity.
 
This listing is for 1 pendulum intuitively chosen by me.