Railgun

Railguns are a type of all-electric weapon that use an electric current traveling down a rail to accelerate a conductive projectile at high speeds. In Warhammer 40,000, the Tau use railguns as tank and walker mounted weapons. In these cases they are very powerful and penetrating (as in real life) as the acceleration is limited only by the amount of power that can be input and how much the weapon can handle with out exploding or melting (in the case of these two, it is quite a lot). The tau also utilize a smaller rifle versions for sniper use by pathfinders, which is weaker but still potent.