Take a knife from your pocket and cut one button of your shirt. Take some buttons of different colors and ask your spectator to choose one of the buttons. You take the chosen button and wrap it using flash paper. Take a lighter and light the paper. When the flash disappears there is no button. Now you keep the attention on your shirt. The red button, the one chosen by the spectator is now on the shirt. But the most incredible part is that it is sewed on the shirt. Resets in less then 5 seconds.
Really easy to do
No difficult sleight of hand
The spectator can touch the button on the shirt, nothing to hide