Lightning Gun: Electrolasers.  Commonly used to stun (which is not as harmless as it might sounds, because, y’know, high voltage doesn’t just stun) and to screw up electrically based machinery.  Work on actual physical principles, involving laser-ionizing a path through the atmosphere for the electricity to be dumped down, and as such are vulnerable to problems resulting from said actual physics, like vacuum, uncooperative atmospheres, and excessive humidity.  And firing them while standing in water or in a metal-lined room is not the smartest idea you’ll ever have, although it might be the last one.