Outside the box FPS weapon

[TheLastSamurai14]

A gun that neutralizes the targets weak nuclear force

Why not one that removes the strong force?

Fucking vapourise them... NO! ATOMISE THEM... NO! SUB-ATOMISE THEM!

Sounds like the Reality Bomb from Doctor Who...

 

[doomspore98]

A gun that shoots napalm filled puppy robots. The puppy walks up to the enemy, you press a button and the puppy explodes, catching the enemy on fire.

 

[Pegghead]

A hose that shoots glue, so not only could you use it against enemies by sticking them to surfaces/each other/ gluing up the barrel of something like a tank's main gun, but also use it yourself barricade the environment, climb up walls and so on.