crystal ball
1. A glass or crystal orb used by fortune tellers and mystics in popular culture to see into the future. The soothsayer, peering into her crystal ball, foretold that I would come to possess a great fortune by the year's end.
2. By extension, any figurative means of predicting future events. She must have some kind of crystal ball for the economy, because every business decision she's made has been timed perfectly to market fluctuations. Well, Mike, what does your crystal ball say about the team's chances in the playoffs?