Self-destruct was a type of ability installed in most 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.

Kahler-Tek had a self-destruct mechanism, which he intended to use when he realised his only potential was as a war weapon, but the Eleventh Doctor convinced him otherwise. (TV: A Town Called Mercy)

Self extermination

A Dalek self-destructs. (TV: Dalek)

Daleks could also self-destruct, 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 used the spherical protrusions from its lower body to form a force field, and to exterminate itself in the end. (TV: Dalek)

In the 22nd century, a group of Daleks on Earth initiated self-destruction after the Tenth Doctor used a proton cannon to make them intangible. (COMIC: Extermination of the Daleks)