Mark Southworth's Double Cross
The trick that gets the single best reactions? Yep, it's Double Cross!
Ask a spectator to hold out their hand and make a closed fist. Pull out a marker and draw an 'X' on the center of your palm and close it into a fist. Now without any rubbing, erasing or funny business, you slowly open your hand and reveal your X is COMPLETELY GONE. Now ask the spectator to open their hand - THE X IS ON THEIR PALM!
The secret behind Double Cross is diabolically clever, and perhaps more importantly, practical. It's always inked and ready to go. There is nothing you need to make or prepare beforehand - just throw the pen in your pocket and you can perform it all night long.