Predict who has the black piece ... or directly predict each and every piece
The mentalist sends an email to a spectator who will act as a notary
Five spectators approach a chess board and while the mentalist is on his back, each one takes a piece and keeps it in his hand. Once done, the spectators cover the board to avoid that the mentalist can have any track.
Under these conditions, the mentalist first guesses the color of the pieces of each spectator, saying who has a white piece and who has a black piece. As a second climax, the mentalist announces what exact piece each spectator has in his hand.
And as a great final, ask the viewer who sent the email at the beginning to open it, finding with great surprise that all actions have been predicted showing which piece would choose each viewer.