Whips were tools primarily used to control animals or slaves.
The leader of the Sycorax invasion of Earth in 2006 carried a energy whip with him, which he used to kill Daniel Llewellyn and Blake. However, it proved ineffective against the Tenth Doctor, who effortlessly caught the weapon in his hand. (TV: The Christmas Invasion)
Robomen carried whips with them to control the Daleks' human slaves. (TV: The Dalek Invasion of Earth)
The Huntsman used a whip to control Lady Adrasta's wolfweeds. (TV: The Creature from the Pit)
Mandrel tried to attack Leela with a whip, but was stopped when Cordo arrived. (TV: The Sun Makers)