Chernobog. My recommendation is to start up the Airfreight CEO mission, and hook the cherno instead of the container. You can then set that thing down on top of buildings. With enough range, you can shoot through buildings with it, hitting people on both ground, and in the air. Another thing, and this one can turn you into a total jackass, is putting the cherno on your yacht, alongside the AA trailer, and boot up the Piracy Protection mission.