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.
Demonstration video here: http://www.youtube.com/watch?v=J6SAxqjxHYk
I have another version that is more optimized for performance and doesn't require you to tape the pennies together, but it is more fragile. I'll try to post that in a few days.
Making instructions here: http://www.youtube.com/watch?v=FlyutldS_44
Non-video step-by-step instructions: http://www.instructables.com/id/Trebuchet-business-card-Trebucard/
Operating instructions here: http://www.youtube.com/watch?v=0lG0HFNvadE
Use a sturdy material like poster-board or the thin cardboard commonly used for product packaging. Then simply print/transfer the design onto the material and cut it out by hand or use a laser cutter if you have one.
The dotted lines are folds and don't need to be cut.
The counter-weights are made by wrapping a stack of 8 pennies with tape and you need two of the counterweights for one card. If you don't have US pennies then other coins will probably work, just find a small coin that fits well in those cutout areas and stack however many it takes to get a firm fit.