Plymouth and Eden already have weapon sets.
Gauss Cannons do not use rails they use magnetic coils. They are AKA Coilguns
http://en.wikipedia.org/wiki/CoilgunThe Gauss would have to be very simular to RPG and Rail in range but would vary in the damage done.
Lasers use Lens and Gas. They dont use crystal. Thats more Star wars light sabers any way. Eden Laser and the Plymouth Microwave are very simular.
http://en.wikipedia.org/wiki/Laserhttp://en.wikipedia.org/wiki/MaserTo make a lasers that has more power you would either put more power through it which would give it a lower ROF. Or use a different base like IR UV Xray or Alpha Beta or gamma rays.
The Magnetic grenade could be seen as the EMP shell that is fired from the EMP turrets. How Ever if there is a way that you can figure out it could use Rail gun technology to cause a powerful concusive blast.
The Rocket launcher is basicly a artillery cannon. No one wants Artillery so its pretty much out of the question.
Ion Cannon I am not so sure about this one.
This blast cannon sound like a normal tank cannon. In which its common place to name it by its Calibur in milimeters.
HE Shot Cannon sound alot like ^^^^^^^ that. dont really need that kinda redundancy.
The Elf Cannon i already tryed this and it was rejected because of how simular it was to thor and because of the name but that could have been changed.
Particle beam Maybe but needs more info.
Plasma blaster has one problem. Ok How is this shell going to keep the plasma stabalized.
Laser Blaster. Not a chance in hell. While possible How are you going to get 3 lasers on a small chassis when only 2 of them fit on a tiger. Making them smaller would make them weak and pointless as some one would have just made one big laser.
Cluster Cannon Possible as they would need atleast one AOE weapon. But i think it needs some work.
Neutron Cannons. I dont know about this. It would be easier to fire Depleted Uranium or just plain old uranium. Getting the Neutrons would be a long and extensive process and would require a Partical Accellerator and enough power to run one.
Please use this
http://en.wikipedia.org/wiki/Wiki to help you refine your ideas.
There are problems with all the weapons though. Having them have super ROF or Super Ranges. Things need a balance and a likeness to the other weapons that exsist in the game already.