Cardiograph

You can use any deck for this trick, which the spectator can shuffle.

Start by asking your spectator to take a small packet of cards, between 5 and 15. Then, take 8 cards while making it random.

Both of you can now mix the cards in your hands as much as you like. You have to remember the 6th and 8th cards.

Now put your packet on top of the spectator's.

Have the spectator deal 2 piles, first to you then to them. Eliminate your pile. Do this until there is only one card left.

Place the last card in the spectator's hand, and do as you tried to read their pulse. Imitate a mentalism trick. You can finally reveal the selected card, which is the 6th or 8th card.