Self-destruct or auto-destruct was an ability installed in many robotic mechanisms. It could be used as a weapon or a failsafe. For many cyborgs and robots, initiation of the self-destruct mechanism was akin to suicide.
The Cybermen created by Missy, the female incarnation of the Master, could self-destruct in such a manner that they unleashed clouds of Cyber-pollen, a liquid metal that would turn organic life into more of their kind. When this substance was released in the skies of Earth, the Twelfth Doctor turned control of the Cyberman army over to Danny Pink, himself partially upgraded, who ordered all the Cybermen to fly into the clouds and conventionally self-destruct, dispersing the clouds and ending the invasion. (TV: Death in Heaven) The only Cyberman who was known to not follow this directive was Alistair Gordon Lethbridge-Stewart, though William Bishop claimed that the former Brigadier had later self-destructed of his own accord. (PROSE: An Ordinary Man)
Daleks could also self-destruct, via self-destruct mechanisms, (PROSE: Prisoner of the Daleks) for various reasons. (TV: Remembrance of the Daleks, Dalek, Asylum of the Daleks, COMIC: Extermination of the Daleks) At the end of the Shoreditch Incident, the Supreme Dalek self-destructed when the Seventh Doctor revealed that Skaro was destroyed. (TV: Remembrance of the Daleks) Another Dalek, who believed it was the last of its kind, asked Rose Tyler to order it to self-destruct after it gained emotions from her. Preferring death to a life with emotions, this Dalek ejected all the sense globes from its base unit to form a force field in which it was completely destroyed. (TV: Dalek) Unknown to the Daleks, their self-destruct would be triggered if they attempted to exterminate Davros. (PROSE: Father of the Daleks)
When the Eleventh Doctor found himself in the Dalek Asylum, a damaged Dalek, deprived of its gunstick, attempted to use its self-destruct to kill him. Before it casing detonated, the Doctor managed to hack into its locomotion systems, sending the Dalek hurtling towards others of its kind, the resulting explosion destroying it and them. Despite bearing the casing utilized in the Last Great Time War, this Dalek's self-destruct lacked the forcefield and manifested itself merely as a large explosion, possibly due to its damaged state. (TV: Asylum of the Daleks)
In the 24th century of a parallel universe, Captain Jean-Luc Picard, formerly Locutus of Borg, and Lieutenant Commander Data were able to induce a Borg cube to self-destruct before it could begin the process of assimilation on Earth. (COMIC: Assimilation²)