Microbomb

Microbombs are small explosives placed on a person's body and set to explode whenever that individual dies, meant only to destroy that specific person's body. They are used to make sure that neither a person's body nor important items can be retrieved by the enemy and were primarily utilized by the Cobra Unit.

Microbombs were activated when the The Pain, The Fear, The End and The Fury were killed by Naked Snake during Operation Snake Eater. The Boss's body did not explode when she was killed by Snake, it is unknown if she ever had a microbomb or hers was removed. Also, as the body of The Sorrow was seen intact by Snake during Operation Snake Eater, it is also unknown if The Sorrow ever carried one, or he had his removed.

Trivia

 * One of the "Secret Theatre" shorts featured on Metal Gear Solid 3: Subsistence shows The Boss being thrown from the bridge with her microbomb activating in a similar fashion to the other Cobra's, even accompanied by The Boss' voice announcing her codename: "The Joy".
 * The main way for Naked Snake to find out about microbombs is to radio Major Zero after a Cobra boss battle; if Snake has fought at least two Cobras, this will begin with Snake asking "Major, why do they keep exploding!?"
 * While the microbomb is designed to destroy the body and personal effects of the Cobra using it, for gameplay reasons a stamina kill still results in that member dropping their Camouflage, except for The End who drops his Mosin-Nagant tranquilizer rifle. To acquire The End's camouflage, the player must hold him up.
 * Although it's stated that the microbomb activates when the individual dies, it's likely that it won't activate if the person dies a natural death, as when The End is evaded for seven days, if Snake catches him, he discovers that The End had died in his sleep, and his microbomb hadn't activated. The scene also implies that a certain amount of pressure is needed to activate the microbomb, as the Parrot briefly lands on him, pecks at his chest a few times, flies off and an explosion occurs.
 * The microbomb will also go off even if Snake depletes the enemy's stamina.