Light Gauss rifle, super sniper or super shit
The standard Spheroid variant is useful on light 'Mechs that want a low heat long range damage option that beats out a standard large laser in range, but it retains the inherent disadvantages of a Gauss rifle — it is heavy, needs ammunition, and is potentially explosive. And to be honest, it is still too heavy to be a good pick for this application over an ER PPC or an ER Large Laser (especially a Clan one, which are becoming more and more common). It also does not do enough damage to truly be worth it.
That said, for a Spheroid weapon, its range and ammunition efficiency are better than the standard Gauss rifle — to have decent staying power on a battlefield, the 12 ton light Gauss only needs a minimum of one ton of ammunition to a standard Gauss rifle's two. This also means that, even when taking ammunition and CASE (which in my opinion should ALWAYS be mounted with a Gauss rifle, especially torso mounted ones) into account, the light Gauss still saves you 4 tons (on a Spheroid 'Mech, anyway).
When comparing the LGR to a Clan Gauss rifle, the advantages only weaken further, since the full size Clan Gauss weighs the same as the LGR. It still needs an extra ton of ammunition, so the LGR still saves a ton over a Clan Gauss, even taking CASE II into account.
It is much better as a weapon for vehicles than it is for 'Mechs, to be honest.
