Here is how I make a simple card transposition stronger and more memorable. The main thing is the glass bit. By turning the glass (thus indicating the transposition), everything is much clearer and impressive for the ordinary spectator, who is distracted by food, whine and the women at the dinner table …
P.S.: This used to be my opener for many years in my table-hopping times. When you do it with a glass from the dinner table, be sure to use an empty one! And yes, I always had a duplicate card in my deck—it made things sooo much easier.