The Psycho-Matic Deck is probably the best force I've ever come across, and if you are on the mailing list then you will know about my adventures in trying to find a stack of them. (Spoiler alert - in the end, I had Stee Short from Gafftastic MAKE me a bunch, and we now carry them on the site. They are AMAZING!)
Anyway, I typed up some instructions for them, and included some killer ideas. However, I totally forgot to include this, which is actually how I used the deck years ago when I used to demo it in the studio.
So, you bring out the Psycho-Matic deck. You show it, let a spectator shuffle, and then have them peek at a card while you look away. They then shuffle again, drop the deck into the box, and you take the box and drop it into your pocket. Only then do you turn back to them.
Looking at them in classic mentalist fashion (eyebrow raised, chin being slowly stroked) you reveal their thought of card, bit by bit. 'It's black. I see a spade... its the Three of Spades!'.
It is, and they love you.
Then, you bring the deck back out of your pocket, and ask if there was any reason they were drawn to that one card. As they consider their answer, you spread the deck face down on the table. In the centre is a SINGLE ODD BACKED CARD!
They remove it, it's the Three of Spades, and then the rest of the deck is clean, regular and ready for more magic shenanigans!
Of course, you simply switch the Psycho-Matic deck for a regular one with an odd card in the centre, which means you can remove it and be left with an examinable, regular deck! BOOM!