The painsaw works pretty much like a chainsaw but it uses energy to cut and instead of wood it cuts alien structures. It was initially designed as a tool but the humans repurposed it after they found out how efficient it is at the latter task.
In game, the painsaw is the weapon with the highest damage per second. It also has a small range that should be reflected by the energy effect. The tool has infinite ammo and only needs an attack animation that can involve the disc at the front spinning.
Concept by alex_bo:
If you want to model it, post here.