For a long time, I’ve been thinking it would be possible to strap a small explosively-formed penetrator (EFP) to a quadcopter. Then you feed the GPS coordinates of your enemy’s apartment or office into the on-board navigation system, and the quadcopter flies over to their place and fires a hypersonic slug of copper through their window.
Leaving aside the ethical concerns, there are a couple of issues with this. The main one for asymmetric warfare enthusiasts is that it destroys your quadcopter and leaves bits of it at the scene, which wastes resources and gives clues to whoever you were trying to shoot.
Then I saw this little post over at Hackaday. If you put a high wattage diode laser on a quadcopter, you can have it set fire to things. It could probably shoot through a glass window and set fire to things on the inside of the window. Once the place is nicely in flames, you just fly the ‘copter away again, leaving no trace.