Tribolting either the Annihilator Anh-5 or the HIG-S Particle Cannon. It's bugged so that they only consume 1 ammo per shot instead of three on those specific guns, while still firing three exploding projectiles. You basically become an explody god and in co-op there were times that I was making so many explosions that both me and my partner were lagging the fuck out. Couple that with eraser cell on either gun and you'll never have to reload ever again.

Same, it's good even on weapons that don't have any damage stacking ability as you can just pump extra upgrade kits into it to fix the damage output (even better if the gun is modular) Though since the P9000 and the SOCOM progressively get more accurate anyway as you enter each room, I don't prioritize accuracy attachments on either of them since they will eventually reach 0 deviation and 0 recoil anyway. It's still worth taking for the magsize increase though.

Reminds me of Alien Swarm: Reactive Drop the way the pre-alpha trailer looks, it particularly reminds me of a campaign level in ASRD where you have to traverse some catwalks to blow up a pipeline that the aliens are using for transport.