The Tubetti armaments Railgun.
Firing Neodymium-Tritium Balls Charged by dual Ionic Lasers, and propelled by Multi-Coil Quadruple stage Ultra Electro-magnets. All of which is powered by a massive Cold Fusion Drive.
The Power of one singular ball is that of a 3 megaton bomb, focused onto one small point in space.
The result is a non-nuclear, low residual radiation, weapon capable of destroying large structures and puncturing any armor.
AND, for those larger targets (Say, a city or town.) the weapon has a variable yeild setting. One shot can actually radiate surrounding atoms. Creating a large ball of fissile material, which can be detonated by another shot.