Something I had imagined, making a gun that shoots a large but very slow moving bullet that can go through just about everything for a decent distance.
Or a cannonball launcher, something akin to the Panzor Repeating Cannon, only making the rounds not explode would be fine too.
Seeing as there is a literal sea of mods, Finding one if it's already made would be difficult.
Though I will still look of course.
I just figured I could toss this out there if there isn't one like it already.

Make a gun which shoots extremely sharp bullets at a low speed and it will "drill" through pretty much anything. If you want the bullet to move in a strait line without falling while it drills uh.... use lua i guess. To make the bullet appear as if it is drilling I'm not sure if you can animate projectiles, but you can definitely make some emitters off of the projectile to make it look like its drilling.

Or you could just, y'know, mod the vanilla rocket launcher a bit, and there you go, insta(ish)-drillgun.

1KG MOSRotating, GlobalAccScalar = 0, optional HitsMOs = 0 if you don't care about hitting Actors and such, just want to drill, attached Lua script:

Stick it onna gun, fired at 10 MPS, presto.