Tweaking the design of his bizarre pump-action Oreo gun, Joerg Sprave has built a smaller version designed to take office warfare to the next level (if the next level is a long two-hour talk with human resources). Made only using stuff you'd find around the office—like cardboard, glue, staples, and rubber bands—the pump-gun is able to fire euro coins, US nickels, or M5 washers.

It's even got a 12-coin magazine so you don't have to waste time constantly reloading in the heat of battle, and the rounds are strong enough to pierce a cardboard box, or leave one heck of a bruise on your unfortunate target. The only catch? Who's willing to waste their pocket change for war when there are vending machines to be pillaged?