Seeing a slingshot in a dream denotes that one of your spirit guides or guardians has been removed to serve a greater purpose. They aren't gone for good, and as most people have more than one guide, it won't become too much of an issue. It can also mean that the guide brings your messages upon their return so be open to receiving new messages.
If you use a slingshot to fire stones or objects at someone or something, this indicates a sign of inner anger and confusion. Using a slingshot in a dream is a sign that you need to meditate on your inner anger and discover its true cause.