Railgun

could refer to: 
*Misaka Mikoto, the Level 5 esper of Academy City, nicknamed Railgun.
*Railgun (ability), which is the official name of her Electromaster ability.
*Railgun (special move), which is the signature move used by Misaka Mikoto.
*Railgun, the first episode of Toaru Kagaku no Railgun S.
*Toaru Kagaku no Railgun, manga/anime series involving aforementioned Level 5, also referred to as Railgun for short.