Microfusion Breeder

 is a type of ammunition in Fallout: New Vegas.

Used in

 * Recharger rifle
 * Recharger pistol

Appearances
MF Breeders only appear in Fallout: New Vegas.

Behind the scenes
From the name it is likely to be associated with breeder reactors, which are a type of nuclear fission reactor that is able to produce more fissile material than it uses.