Fusion pulse charge (Fallout 3)

The Fusion pulse charge is a device used to detonate the nuclear bomb in Megaton. It is given to the Lone Wanderer by Mr. Burke in Moriarty's saloon. It is unknown how it works, but the name might suggest it sends some sort of pulse which activates a fusion reaction in the bomb and detonates it, resulting in a dirty bomb.

Detonator
The detonator of the fusion pulse charge is set up by Mr. Burke on Allistair Tenpenny's balcony. With its characteristic glowing red button, it is used in order to activate the charge and detonate the Megaton bomb. Mr. Burke gives the "honor of pushing the button" to the Lone Wanderer.