The Black Project Drone. That's for the look, a bit less for the practicality (the link between the sphere and the nose can be easily broken). In terms of practicality and of resistance to injuries, I would then choose the Police Drone.
I like the military drone the best. It's worth noting that you've done a great job with each of these in conveying the purpose of the design. For example, the police drone really looks like something a civilian police force would use, rather than the military.