BB

 are a type of ammunition in Fallout, Fallout 2 and Fallout 3.

Fallout and Fallout 2
BBs are going to be a very useless ammo type to most characters. They're heavy, they're rare, and 2/3rds of the guns that chamber them are useless compared to the starting guns. However, if you run across Bob's Pre-owned Car Mart, or revive Dobbs in Sierra Army Depot, you might find the Red Ryder LE BB Gun, which makes BBs a useful ammo type.

Weapons using this ammunition

 * Red Ryder BB Gun
 * Red Ryder LE BB Gun
 * Jonny's BB Gun

Fallout 3
BBs are a small guns ammunition found in Fallout 3. They are used in only one weapon, the BB gun.

Locations

 * On top of VAPL-58 Power Station: a gun and 3 ammo containers.
 * NW from Scrapyard there is a power station. The first power pylon south of it has a gun and 2 ammo containers.
 * 300 rounds on the assembly line of Mothership Zeta Cargo Hold section.
 * Over 100 to the right on a shelf next to 2 BB guns just before you enter Haley's Hardware (Point Lookout)

Fallout: New Vegas
BBs are going to appear in the upcoming game Fallout: New Vegas. 

BB Śrut