The versatile Taper Cards
Many routines are possible with the Taper Cards - here's one;
Have a card selected, remembered and returned to the deck.
Now shuffle half the cards face up and half the cards face down. What a mess!
That would take ages to sort out, but not fo you - the most incredible magician the world has ever seen.
A simple cut of the cards and all the cards are back facing the same way. All except one that is - you've guessed it, their card is the only card face down in a face-up pack. A true miracle!