Misaka Mikoto

Mikoto is a main heroine in Toaru Majutsu no Index and the main protagonist of Toaru Kagaku no Railgun. She is the third ranked Level 5 esper in Academy City, and is nicknamed "the Railgun" due to her signature move. Her ability belongs to a type of esper powers known as Electromaster: those who can generate and manipulate electricity. Being the strongest Electromaster in the Academy City, her maximum output is known to be 1 billion volts.
To most people, she is considered a 'proper lady' (referred as ojou-sama), but in reality, she's short-tempered, prideful, and has an improper attitude with some slight tomboyish tendencies and insecurities, a fact few people know of. Despite this, she is generally friendly and easygoing, and Saten and Uiharu comment on how they are shocked to find that, compared to other Level 5's, she doesn't look down on lower-level espers at all. This is probably because she was originally a level 1 esper and became a Level 5 esper through very hard work.
Often times she shows an incredibly immature and selfish side and even slight tsundere tendencies when her crush, Touma, insults her. To add to this childishness, she has an inclination towards cute things, most specifically, Gekota and Kill Bear merchandise. She likes frog merchandise, but only if it features Gekota.