The Trebucard is a business card sized mini trebuchet. It is designed to fire jumbo paper clips and uses 16 pennies as a counter-weight. Unlike a traditional trebuchet the Trebucard uses the surface it is resting on as a pivot rather than being mounted on a frame.
See a demonstration of the card here:
And here is a video that shows you how to make your own:
Step 1: Download the design files
Download the design files for the card in whatever format is easiest for you to work with.