Pendulums are divination tools, used to answer yes/no questions to assist in providing direction.  They work by responding to your subconscious mind.
 
Unakite
Associated with 3rd Eye Chakra
Unakite helps to free one of negative energy of past events or traumas and find peace in the present.  This is an excellent stone if you are looking for grounded power in your queries.
 
This listing is for 1 pendulum intuitively chosen by me.