You hand someone a deck and take one yourself. Everything you do, they do — shuffle, cut, take a card, remember it, bury it. Nothing is said and nothing is shown. Then you both turn over the card you took, and they are the same card.
There is no sleight of hand and no setup. It works with two borrowed decks and it fools people who have watched it before, which very few tricks do.
How to perform it
Two decks. Both get shuffled, by both of you. Genuinely — let them shuffle yours and shuffle theirs. It costs nothing.
Swap decks. As you hand yours over, glimpse its bottom card. That is the only secret move in the trick and it happens once, in the open, while everybody is busy swapping.
Both take a card, look at it, and put it on top. Say it out loud as an instruction so you are mirroring, not directing.
Both cut the deck and complete the cut. This is the move that does the work. Their chosen card is on top; the cut drops the rest of the deck onto it — and the bottom card you glimpsed lands directly on top of it.
Swap back. You now hold the deck containing their card, marked by your glimpse.
Find "your" card and take it out. Look for your glimpsed card and take the card immediately below it. Put it face down on the table without a flicker.
Turn them over together. Same card.
Why it works
Because a cut does not shuffle — it moves a boundary.
When they put their card on top and cut, everything below the cut point goes on top of it. The card that was on the bottom of the deck is now sitting directly above their selection, and it will stay there no matter how many further cuts anybody makes.
And the mirroring is the misdirection.
Every instruction you give applies to you too, which means nothing you say sounds like a condition. People look for the moment the magician did something. There is only one, it lasted a second, and it happened while two decks were changing hands.
Making it play
Never say "remember your card" and then look at your own. Do everything simultaneously. The whole effect is that you had no opportunity.
Let them shuffle as much as they want, before the selection. After the cut, more shuffling destroys it — so build the routine so there is no natural moment to shuffle again.
If they cut more than once, you are still fine. Any number of straight cuts leaves your key sitting on their card. Only a riffle shuffle breaks it.
More
All of these, with the ones you can deal through on screen, are on the
self-working card tricks page.