All you need is a square of paper and a few spare seconds.
Step 1: To Make It
Fold the square diagonally in half.
Fold a crease from one end of the first crease to the corner.
Open up, and refold, this time with the smaller section wrapped around the outside of the larger section.
Step 2: Flapping.
Repeat until bored.
Give to small child or office manager.