The Trick That CAN Be Explained! by Mark Elsdon
The performer introduces a small envelope and says that there is a playing card inside. He places the envelope on the table and never touches it again. 

A participant takes the deck out of the box and shuffles it. Then they cut the deck and the top card is immediately turned over. It is, for example, the 7 of Spades. The deck is turned face-up and clearly spread to show that there are no duplicates. 

The participant opens the envelope and removes the card inside. It is a perfect match - the 7 of Spades. 

AND THERE ARE NO OTHER OUTS - the card in the envelope is ALWAYS the card they choose! 

NO sleight-of-hand required. This literally is as easy as it gets!