Railguns as
weapons could well see use in space-based platforms, since the
airless environment would dramatically improve their efficiency. Such craft would mostly be used for destroying enemy
sattelites, I would imagine.
The pressure difference of the gas-injection system would be maximised by the pressure gradient with a vacuum rather than atmospheric pressure, the resultant increase in muzzle velocity would be useful if not vast.
But more importantly, you don't ionise air and fuse the rails when there's no air to ionise, so the railgun, along with being supercooled, can operate far longer and over many more shots without maintenance.
They even become, technically, semi-automatic when used in such circumstances.
NASA is already considering railgun technology as an alternative method of launching supplies into space, although at the moment costs remain prohibitively high.