Time bomb

Metal Gear Solid
Solid Snake will receive an unwanted gift from Revolver Ocelot known as the Timer Bomb when he grabs his items after being tortured in Metal Gear Solid/The Twin Snakes. Small enough to fit into a back pocket, this is usually placed in a dummy item and micro-wired with enough plastic explosive to destroy a light tank. This bomb can be mistaken for for a keycard, magazine, or ration to the untrained eye. Nanomachines automatically detect the timing device, and can inform Snake about it. The time remaining until the bomb explodes can be seen in the inventory display, which is about 1,500 seconds. Another time bomb can be found in REX's underground lair by using the Mine Detector. This one goes off after 30 seconds have passed. Both should be thrown away immediately. Colonel Campbell then calls Snake to tell that "that was a close one" after the first bomb. Note that if Snake failed to check his bag by the time he gets to the Communications Tower, Gray Fox (under the alias of Deepthroat) will contact Snake to warn him that he is carrying a timed explosive.

Metal Gear Solid: Portable Ops
The Timer Bomb is created by the player's technical unit and simply planted at the required location. This is used by the player to sabotage the switchboard to the Silo Entrance door that is locked electromagnetically. Campbell and Naked Snake have found it unfeasible to sabotage the switchboard at the Substation immediately with explosives such as TNT as they only have 5 minutes to open the door at the Silo Entrance manually and instead require a delayed explosion and the right timing. Waiting too long will get Campbell mad and another Timer Bomb will need to be created to sabotage the switchboard again.

"A bomb equipped with a detonation timer. Explodes after a set amount of time upon being planet."

- Time Bomb weapon's description from Metal Gear Solid: Portable Ops