Hair Whip (sometimes called Ponytail Whip or Hair Slap) is Shantae's trademark move and her main attack in the series. Shantae can use her long purple ponytail hair as a weapon, cracking it like a whip by shaking her head.
It was revealed in Shantae: Risky's Revenge that this skill is not a by-product of her genie half from her mother's side, as she is still able to use this ability after her powers are removed. While it's possible that this ability came from her father's side of the family, Mimic theorizes that Shantae has her own, non-genie magic that lets her use her hair this way. As Nega-Shantae isn't seen using the Hair Whip at any point, both theories are plausible.