You would be surprised what a suitable slingshot loaded with ball bearings will do to a light weight plastic or metal frame. What it will do to cameras, sensors, and drone rotors is *dramatic*. The best part, though, is the price.
Lot of remarkably cheap and available solutions for killing robots, should robots ever become a peril to the operating of a free and just society. Fine sand or 70% isopropyl alcohol poured into openings in the chassis, intakes, cooling grills, for instance.
Both bipedal and quadrupedal machines cope with a total loss of traction remarkably poorly. This can be facilitated in multiple ways, from the prosaic (a floor or tarp covered in petroleum jelly - also flammable!) to the comedic (several thousand cats-eye marbles)
What's your favorite method for killing robots or drones?