Pendulums are divination tools, used to answer yes/no questions to assist in providing direction.  They work by responding to your subconscious mind.
 
Green Aventurine
Associated with Heart Chakra
Green Aventurine is a great stone for working on prosperity and abundance.  It also helps to connect the heart with the earth.  This would be especially helpful in questions relating to financial health.
 
This listing is for 1 pendulum intuitively chosen by me.