The Fermion Shock is a rather large wave type gun. (The player does not see the weapon during game play per se, only that the color has changed).
The Fermion Shock is a short range, wave like blaster. It is best applied against entities with a yellow energy aura. The shock wave displaces the entities' resonance field. 
- On page nine of Ghostbusters Issue #3, the Fermion Shock appears on the shelf rack.