Here's an entire routine with multiple surprises for your audience! And it's fun to do!

EFFECT:

The performer takes a deck out of its case. He spreads it face-up on the table. The deck is now squared and put aside.

The performer pretends to shuffle the deck invisibly. He pretends to take the deck (in fact, the deck stays on the table and he acts as if he had the deck in his hands), put it on the table in front of him, cut it in half, turn one pile face-up and shuffle both parts with a riffle shuffle, square the deck, take it, and put it back where the real deck was.

The deck is spread on the table, and all the cards are mixed, half face-up and half face-down, as if these fictitious actions became real.

The deck is put aside. The performer separates the cards in the same way with an invisible deck in his hands and then puts it back. The real cards are spread, and all the cards are face-up again. He squares the deck and puts it face down. He then spread the cards, showing that only the card backs are visible.

The cards are squared and taken with the right hand. The face card is the Queen of Hearts. The performer does a magic move and spreads the cards again, showing that now ALL of the cards are the Queen of Hearts!

Squaring the deck again, the performer does another magic move and spreads the deck to show only ordinary cards. He then spreads the other side to show only the backs of the cards!

The performer puts the deck back in its case and closes it. As he puts it away, he changes his mind and hits the short side of the case, showing that the image on the front of the case has become compressed.

Comes complete with gaffed card deck and detailed online video instructions on how to perform this trick.

The Deck That Shuffles Itself (Gimmick and Online Instructions) by Dominique Duvivier