When I come across weapons associated with Nanotechnology, the first that often shows up are Molecular Disassemblers, or what others would like to call Grey Goo.
Molecular Disassemblers utilise particles that can break down any material at a molecular level. Many have often confirmed that nanotechnology can allow for its existence.
However, I have never seen actual proof of its existence, though there is no proof of it being impossible either. What is more, small-scale molecular assemblers have been already created.
Thus I have to ask, if such particles, both biological and mechanical, and allow such a weapon to exist.