SOCKS is simple and strong in premise: you display two packets of cards with different sock designs on each one. You explain the premise: the spectator will choose two socks, and you hope that the spectator can find the only perfect match. Turning them over, two at a time, you show that each pair is mismatched. When the spectator says stop, you place their selections to the side, face down.
The spectator turns over the two chosen socks to reveal they do NOT match at all: yellow stars on one sock and purple stripes on the other. But you then lift up your pant cuffs to reveal that YOU ARE WEARING THE EXACT SOCKS THAT THEY CHOSE. This hits people hard and comes as a complete surprise. It's not a card or coin or rope trick, either. It's a mentalism piece with an article of clothing, and something everyone can relate to.