this is not for sharing your destroy the world plans, nor is it a comparison of already created weaponry, it is either an invention of something new(just a rough sketch i don't care for blueprints), or a nice combination/improvemtn of weapons that already exist, this is my first entry:
this is modeled after the "airport in the sky" from ace combat 6 that i heard about, but all i really take from it is that i've got one bigass plane.
said plane is to be aproximately the length of an aircraft carrier, slightly wider, slightly less long, and far less thick from top to bottom, i'd say it would be 300m long, 65m wide(not including wings), and 15m tall. were it a solid cube(which it is not, it is more aerodynamic, and has wings) and made of pure steel(which it is not, there is air inside for the crew and troops, and various other less dense metals used for the weapons systems and reactors) then the ship would weigh as much as 2.3017995*10^10 newtons, this would require an equal and opposite force to lift, thus the thrust to remain afloat would be aproximately 25billion newtons
(if my math is incorrect here then please inform me of such so that i can fix it, or if you feel the desire, then fix it yourself)
in order to supply this force containted therein would be five cold fusion reactors wich draw power by taking the strong nuclear force from the nitrogen in the air and turning the nitrogen into iron generating about 175 million joules of energy per reaction each. there would have to be aproximately four reactions per second in four of the reactors just to keep the ship afloat and moving at a snail's pace forward, this means that a mole of air could fuel the propulsion system at low speed for over a day and seeing how the amount of air that the plane would be exposed to is virtually unlimited, it would not be foreseeable for this process to ever "run out of gas". one reactor would go to powering each of the four wings described herebelow:
the propulsion system is similar to our current nuclear reactors in that power is gained from heating a fluid which expands, then driving a turbine, however that is where it stops, because we currently use water that runs through the turbine which runs a generator, however this system takes in strait air from the front and uses the nitrogen to fuel the reaction while the remainder is forced through valves heated by the reaction, these drive the turbines which drive four(that's how many i think it will take, it may be more) turboshafts(essentially helicopter blades surrounded by a tube that improves effeciency) on each wing. the turboshafts normally should be pitched at an angle that is such at 16 reactions/second that it provides just enough upward force to keep the plane afloat and the rest is used for forward propulsion, however 16 reactions/second is just not possible, it's too few to really make happen, it would be more along the lines of 400,000 reactions/second, so with cold fusion, you can get a plane with dimesions similar to an aircraft carrier cruising pretty damn fast(above mach1 is fast for something this big, and this thing could go around 245Km/H).
this is just for the first 4 reactors, that extra reactor is running at a similar rate and thus is producing 100,000 reactions per second, this energy is used for everything else the ship could ever neeed and use, from weapons to defense to communications to running the ship's onboard supercomputers used for precision targeting of weaponry and calculation of the tragectory of conventional weapons.
the main defense systen that this ships is designed to carry is an series of up to 100 externally mounted railguns that use electromagnets powered by the reactors to lauch low mass solid projectiles at incoming misssiles and/or airborn threats such as fighters, bombers, and interceptors.
the weapons system would be whatever doomsday device you damn well feel like putting on it, from you ion cannon, to a high powered laser, to a bigass version of the railgun that can create a shockwave when it hits the ground strong enough to shake a city to the ground, all that and more is possible with the one reactor i left for weaponry.