Pendulums are divination tools, used to answer yes/no questions to assist in providing direction.  They work by responding to your subconscious mind.
 
Iolite
Associated with 3rd Eye
Iolite is a great choice for focus and communication.  Helps to uncover hidden patterns and show you the way if you're feeling lost.
 
This listing is for 1 pendulum intuitively chosen by me.