[1-more]

They sell adapters to turn oil cans into silencers. Each one should be a violation of the National Firearms Act and subject to up to a half million dollar fine https://www.atf.gov/media/25071/download Nota bened; these are not per-se illegal, but you need to sell them through a firearms dealer and pay for an ATF tax stamp and only in states that have not banned them/all NFA items.

[thenthenthen]

This. Same for the Chinese mainland app, some wild stuff like that being sold (firearms are highly regulated, but 1:1 copies seem to be ok, maybe because of the high level of regulation?)

[gambiting]

And hundred-watt lasers sold as "obstacle removers" that can blind people in less than a second from considerable distance.