(washington dc usa)
Effect: you ask a spectator for a pad and a pencil, and write a number down on the sheet, then ask the spectator to tell you the number you have written down. they pick, say, 78. you turn the pad around and 78 is written on the sheet!!!
The Secret: you have a small tip of a pencil taped to the top of your thumb, and as they choose a number and say it, you write it down with the pencil on your thumb.