This is like something out of a nightmare: a chainsaw attached to a drone. What could possibly go wrong?
A couple of Finnish farmers went and attached a chainsaw to a drone, and showed off just how scary the robot apocalypse could be.
Now, given that this was published on March 31st, we're more than a little sceptical of this video: it could easily be an early April Fool's day prank for the internet. That's a heavy saw on the drone, and we're not convinced this is real.
That all said, and while it's an utterly terrifying thing to watch, this does show some really practical uses for such a contraption. Taking down branches from tall trees would be a really useful tool for power companies, trying to clear lines, or similar functions.
That said, this does answer a question that Mythbusters answered a while back. During my talk with Adam and Jaime for that article, Hyneman noted that he had done something similar: he mounted a circular saw on a drone to trim branches really high up. So, it's certainly a plausible video.
Fortunately, it looks like all we need to defend ourselves are balloons: lots and lots of balloons.