Currently all energy weapons deal energy damage, it pretty obvious that that energy weapon require energy mount.
Graviton Beams. Also, I tihnk the problem Gothars has brought up has been misunderstood. He's saying that it is potentially confusing to have a damage type and weapon type have the same name, especially in cases, such as the Graviton Beam, when energy weapons are not doing energy damage, and when non-energy weapons are doing energy damage, such as the Mjolnir Cannon.
I think what we need here is some consistency across the systems. The weapon and mount types are, for the 2/3rds majority, named for the delivery method of the damage type (ballistic weapons fire shells, missiles fire self-propelled explosive, and neither restrict what kind of damage you would assume the weapon can do). Energy works just fine as a damage type, but does not very well describe the delivery method of the damage.
Since nearly all vanilla energy weapons use beams or lasers, beam weapons/mounts would be a suitable replacement I think.