-Antimatter weaponry, could use positrons ( anti-electrons ) to de-stabilize the atomic structure of target matter, virtually annihilating it. Requires evolved version of the CERN TRAP project to contain and stabilize antimatter particles in a safe way. Direct hit to containment system would of course destroy the surrounding area.
Info on CERN:s antimatter research can be found here.

-Optical and Radar transparency, cloak. Evolved version of current radar-trancpareny systems combined with optical re-direction technlogy to achieve non-detectable craft.

Hope you got some ideas, this was just what I could think of right now, I''m sure there''s a lot more realistic/semi-realistic technolgy to use in games.

------------------
It''s me again!

Hovertanks... hmm. Well, the most obvious way would be vectored thrust, which can easily generate enough lift to carry a tank (assuming you have the fuel, but there are more interesting ways. You could try a super-high-current-carrying superconducting coil aligned such that its field opposes the electromagnetic field of the planet. Of course, this involves huge amounts of energy.
Another, perhaps more interesting, method is a spacetime warp. What you may want for this is another superconducting coil, this time carrying far higher currents. The photons in the focus of the coil will "coalesce" into a kind of super-massive particle. The mass of the particle bends space and creates a gravitational field of its own. If the field is directed upward, the gravitational force of the particle will lift the tank. Turning the current on and off quickly would prevent the tank from colliding with the particle above it.
This method isn''t scientifically proven, but theoretically (according to one theory, anyway) it should produce the effect you''re looking for. The theory is pretty simple, but the specifics get complicated, so there are a few holes in the method for which fixes are too complicated to discuss here, but it just might serve your purposes. Glad to be of assistance (assuming that this is useful, of course).

Well, why don''t you guys take some time and reverse-engineer the motion behaviors you want the tank to have, and see if something similar exists in the world today. Every complex system that works evolved from a simple system that works (paraphrased quote).

Hovercraft in general get the majority of their control from the (surprise) control fans. The rest is skirt friction, which is what keeps the vehicle from being generally frinctionless and therefore almost impossible to control (Try writing a true zero-g sim where you can only ADD energy, and it escapes at a very low rate, and controlling your object).

The advantages of near-frictionless motion are things like slewing, circle-strafing, and near-instant moments of acceleration. The disadvantages are fine control, because you''re only pushing air against air, and air is not very solid, after all.

Do you want the vehicle to be able to stop or turn on a dime? How about switch from forward to reverse? Is the vehicle stationary when it goes hull down?

A lot of what you seek can probably be thought of as a jet-ski simulation, sluggish acceleration in any direction, but highly maneuverable once it gets going.

As far as the propulsion tech? There isn''t a realistic solution for the power/weight ratio I think we all generally expect from H-Tanks (like the ones the Robotech Fighters used during the Invid occupation). Personally I''m thinking that once we get controlled, sustained fusion, we''ll have mini-tokamaks in somethine like that. It can shut down clean and fast (and defensively!!) by dumping it''s containment field and venting all the plasma out the front, toward the enemy. Imagine having a couple kilos of nuclear furnace barfed at you at railgun velocities! That should solve a lot of your collateral damage from anti-matter drives, and give you a good fuel/power ratio. Once you solve the power problem, the sky is pretty much the limit, but my bet is vectored (airfan or plasma) thrust with a magnetic or reaction (rocket powered) cushion.

Oh yeah!! I just remembered that there''s a bunch of plasma-drive tech in use by NASA/JPL for some deep space propulsion systems. Essentially a b-field draws a charged particle out of it''s energizing shunt to strike or pass through the acceleration grid. Thrust results from the particle passing the pinch of the accel grid. Maybe I''m way off, but after fusion, the power available increases a lot.
---------------
-WarMage
...but again, how much would the SC-magnets for the hohlraum weigh? Anybody doing fusion chamber work?

Could it be as simple as some kind of force field, or a tractor beam that pushes rather than pulls, allowing the hovertank to hover when the field is engaged? I don''t know how scientfically feasible that is, but it would probably use less fuel than vectored thrust.

I don''t know how scientifically plausible this is but it''s an idea. For a power supply there could be some sort of fission/fusion reactor. Fission would split the material and create energy. Once the energy is spent it would switch to fusion which would bond the newly formed elements together again creating more energy. Feul would last much longer. Not an endless supply mind you since some of the matter converts to energy but a lot of it would be reused. Like I said it probably isn''t scientifically accurate but hey, this is a game. And set in the future no less. Just a thought.

About antigravity: In a Bose-Einstein condensate, all the particles are aligned on parallel axes. This can also be done in a single plane, with all the axes perpendicular to the plane. Then, using controlled laser bursts, each one of these particles can be made to spin in the same direction (much in the same way lasers are used to stop spin and reach near-absolute-zero temperatures nowadays). Each particle exerts a small gravitational force (towards or away from itself), but, given a large enough plane (and perhaps multiple layers), a significant gravitational field can be created that extends in the volume directly above or below the plane perpendicular to the plane into infinity (although it, like light, does have falloff).

A plane of this specifically manipulated Bose-Einstein condensate could be attached to the bottom of a tank, and would be able to lift the tank to an arbitrary height off the ground dependent on the speed at which the particles are spinning and the area of the plane of them.

Most importantly, I''m not making this up. It was in either Popular Mechanics or Popular Science a few months ago.

Woah.