I voted that drone strikes are the worst, by far.
And let's be clear - drones were developed by the military as a tool of war to be used in war zones where military personnel could not go safely and to enhance tracking of enemy forces. They were only armed, later in the process, in order to facilitate attacks on enemy forces where military personnel could not safely and competently go.
Like many things in government, what once was a great tool of war is now being bastardized and rolled out for any number of other nefarious uses. Drones are now being used to spy on activity of citizens, not enemies. Drones are being sold to corporations and rich individuals for use beyond our control. I'm pretty sure waterboarding is not going to be used on the shoplifter at the local mall anytime soon or by corporations to fight corporate espionage.