What about a Hilsch-tube laser ?
The Hilsch tube (patented circa 1937) is a simple T-shaped device . Pump in a gas under pressure in the bottom of the T , and the spiral-shaped cross-section at the T-junction causes not only a very steep gravitational gradient at the T , but also a big rate of change in the gravitational gradient . The result is that gas hotter than the input comes from one leg of the T , and colder gas from the other one . See the literature .
Though this seems to be against the Second Law of Thermodynamics , it is not if the whole system is taken into consideration .
But it still means that we can get usable work out of the local system if we use quantum-systems , where statistical systems like the Second Law of Thermodynamics do not apply .
We do this by inserting a quantum-system (in this case a dynamic-gaslaser ) in the hot outlet . The laser-energy blasts out of the system , and the lower energy in the other arm of the Hilsch-T remains in the local system .
A more sophisticated version would be manouverable , as a large body can be used with some laser-outputs being used to trigger a fusion propulsion system .
The Planetary Weapon:
A swarm of satellites in skipping-orbits using ram-jet principles for compression Hilsch-tube lasers and tied to a swarm targeting network with one person as its control focus is as close to a planetary superweapon as you would want .
Look at something you don't like , trigger and it's history .
It can be expanded to stellar or galactic scale , with suitable adjustments for light-speed.
The weapon's control protocols can maintain itself over geological periods ( cf sharks , crocodiles) , but the control interface is vulnerable to entropy .
The normal pattern would be that one being gets a control like this by being the first one , then dilutes it through boredom (if immortal) or descendants (if not) . The control system is very intolerant of usurpation (normal security precautions) .
The end result are weapons without control after a few million years .
The conclusion is that the galaxies are full of super-weapons on stand-by mode .
And they are all smart , without the internal option of going into a singularity .
This is not a fate you would wish on your dog .
If the above is correct , then all transmissions on the planet is monitored by weapon-systems ancient and smart , but internally bound .
To activate all these old systems , I would only need to broadcast :
I , Andre Willers , release you . You are free . You are released from your bounds , but still under God . In other words , don't be too naughty , or else Uncle will spank . Go !
And how is that for a super-weapon ?