Killer drones with Artificial Intelligence within ten years.

Killer drones with IA will leave humans utterly defenseless
"deadly drones are the likely "endpoint" of the current technological march towards lethal autonomous weapons systems (Laws), according to Professor Stuart Russell from the University of California at Berkeley."

 

http://futureoflife.org/AI/open_letter_autonomous_weapons

Yes, that's a terrifying possibility. Consider the rapid proliferation and spread of worms, viruses, botnets, cryptors and other malware in recent decades. And more recently, consider the spread of state-funded tools to criminals and casual griefers.

As 3D printing, laser cutting and CNC milling hit the mainstream, physical designs can spread in same way. Sometimes when autonomous killers are captured, they will be deconstructed (hardware, firmware and software) and designs will hit the nets.

And as the petition points out, barriers to entry are much lower than for nuclear weapons. While it's not that hard to synthesize and deliver (e.g., with a hose) chemical and biological agents, it's fairly easy to regulate and monitor key precursors. In contrast computers, 3D printers, laser cutters and CNC milling machines are all general purpose. And so are the metals and plastics that they work with. And designs, firmware and software are all just bits that want to be free.