How about drones killing drones? If I considered drones a real threat, I would certainly have a complement of anti-drone drones to take them out.

Or maybe some RC airplanes,

Or maybe a kite...kites can be deadly too.

Hmm, looks to me like this could escalate relatively quickly.

Just sayin'
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The ultimate result of shielding men from the effects of folly is to fill the world with fools.
-- Herbert Spencer, English Philosopher (1820-1903)