Alright, this is my first attempt at creating a standalone weapon concept, so you'll have to bear with me.
Appearance:
A pulsating rifle with tentacles writing at the base of the handle and along the bottom of the barrel. The rifle's midsection is covered in large swathes of infested flesh, with 6 pores pulsating at the top. The weapon's pulsating intensifies as its passive (explained below) stacks. Additionally, the pores squirt out infested guck when reloading. Yum!
The Main Gimmic