Quantum-tipped time bullets were a type of bullet which could be used to shoot an individual and then un-shoot them. Time around the bullets could also be slowed down or sped up by their user.
The Headhunter fired quantum-tipped time bullets at Lucie Miller's head in order to temporarily incapacitate her during the journey from Blackpool to Orbis. One bullet remained inside Lucie's brain, temporally frozen; the Headhunter threatened to unfreeze the bullet if the Eighth Doctor did not cooperate with her. The bullet was later removed. (AUDIO: Orbis)