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Double stick tape is also known as double sided tape. A little piece can achieve big miracles. If you do not use double stick tape in your repertoire then you're missing a powerful weapon.
Take a small piece, about half the size of a postage stamp, and stick it to the back of the top card on the deck. Press your finger on it several times to remove a little of the 'sticky'. Have a spectator select a card from the deck and drop it back on top of the deck in your hand. Say something like "We will put your card back on top of the deck", as you tap the top card with your forefinger at about the point where the tape should be on the card beneath. Do this to thoroughly stick the two cards together. Make sure they're square.
You can now go in a hundred different directions. For all practical purposes, when you turn the top card over, the spectators card will appear to have vanished from the top of the deck. If you drop the top card face up on the table, quickly drop several other cards face up on top of it. Then, ribbon spread the remainder of the deck to show that the card has completely vanished from the deck. If you forced a card to begin the effect, you can have a duplicate in the card case, and show that the card has vanished from the deck and reappeared in the case.
There are a gazillion different moments you can accomplish with a small piece of double stick tape. Try it out.