A crude single-shot launcher assembled from plumbing pipe, a shotgun firing mechanism, and whatever propellant the builder could acquire. The Thumper fires improvised projectiles — typically tin cans filled with scrap metal and a detonator, or repurposed commercial firework motors with fragmentation sleeves — at ranges between 20 and 100 meters with accuracy best described as 'in that general direction.' The weapon is dangerous to the user nearly as much as the target, with a failure rate that discourages repeat engagements.

Thumpers appear throughout the Shelf whenever tensions escalate to the point where residents feel the need for area weapons. They are built in garages and basements from materials that cost less than Φ50, and their improvised munitions are assembled from similarly available components. The weapons are terrifyingly effective despite their crudeness — an explosion doesn't need to be precise to be lethal, and a can full of scrap metal detonating in a crowded space achieves the same result as military fragmentation at a fraction of the cost.

Every Thumper is unique. There are no production standards, no quality control, and no two weapons that fire the same way. Operators learn their weapon's specific quirks through practice — how far left it pulls, how much the propellant charge varies between shots, whether this particular pipe has a weak seam that might split on the fourth firing. Using a Thumper is an act of faith.