If you want to see their jaw drop try this effect.
Performer shows a small card wallet. Each side has an oval cut out of it. Through one oval the blue back of a playing card is visible. The spectator selects a card from a red deck (say the 4 of clubs) and this is inserted in the other compartment of the wallet without being shown.
On turning the wallet around it is seen that both cards match. The performer gets the spectator to sign the back of the red card and taking the card out of the wallet he places it face down on the spectator's palm. Explaining the unlikely event of this happening, the performer takes a second card from the deck. This card suddenly changes to a blank card. As if in sympathy the spectator's card also now has a blank face. The spectator is given the signed card as a momento.
The wallet does the switching for you. You will perform this within two minutes of receiving it. It is a reputation maker. Use your own playing cards.
Difficulty Level: 1 - Basic Sleights / Self Working
Artist(s): Charles Gauci
Additional Requirements: Blank Faced Deck