Tesla Cannon

The Tesla Cannon is a shoulder-mounted directed energy weapon.

Background
 The Tesla Cannon was designed by the U.S. Government, as a sister project to Poseidon Energy's Solar Cannon and served as a lightweight, anti-tank energy weapon. The cover of Future Weapons Today mentions them being "light and compact". During the conflict between the Brotherhood and the Enclave in the Capital Wasteland, Brotherhood scribes worked to build their own Tesla Cannons utilizing a Tesla coil to more effectively counter the Enclave's vertibirds. 

Behind the scenes
The Tesla Cannon was planned for the canceled Fallout: Brotherhood of Steel 2.