I think an "acid" weapon would be a nice addition to the game, if you mean what I think you do: acid, like poison, a damage over time weapon.

I have no idea what you mean by "fusion weapon" can you elaborate on that?

But yeah, a damage over time weapon would really invigorate the gameplay, add another dimension.

3 types of weapons is enough although a damage over time weapon should be added to any of the three already existing types of weapons for example- Acid Shooter A for physical Acid Shooter B for explosive and Acid Shooter C for electrical

Maybe we could something like an dark matter class of weapons. The point is that this game could use some more variety, cause everything is so predictable.