Ravashol pulsar
From Battlestar Wiki, the free, open content Battlestar Galactica encyclopedia and episode guide
The Ravishol pulsar, developed by Dr. Ravishol, was actually intended to be a peaceful but powerful communications device that transmitted information through laser energy.
The Cylon Empire captures the gun and converts it into a very powerful weapon.
Captain Apollo leads a band of Colonial Warriors to the gun and destroys it (The Gun on Ice Planet Zero, Part II).