Cunts can't kill you when they're flat on their ass
 Arbites Build - Warhammer 40k: Darktide 

As the title says, you're here to knock over every close range threat to your team that isn't a monstrosity. Ragers? Bitchslapped. Maulers? Spear tackled. Bulwarks? Swee- uh, Grenade the leg. Crushers? Woe, electric head bop be upon yee. Everything else just mash left click till they stay knocked over. 

(you may ignore the following paragraph it's mostly rambling and justifying suboptimal choices)
Just one problem... Gunners are a pain. If you don't have a vet or psyker prioritizing ranged threats for you, no amount of gunner resist curios will protect you from those 3 generic gunners you didn't notice when the melee chaff clears up.  And you could easily solve this problem by using either of the arby specific range weapons, and feel free to do so, but I tend to try and make my builds as different as possible. I already have a shock maul+shotty build and a shield melee+shield range build so I didn't want to use either of them again. The various auto guns felt like it was encroaching on what I see as the vets territory (can you tell I'm somewhere on the spectrum) and the heavy hitters such as revolvers and bolters are just a tad too slow dealing with multiple ranged.

SO. I noticed the Walk It Off node. I noticed the shredder had Inspiring Barrage. AND I found out (after 900 hours) that the shredder can always be fired while sprinting, without requiring Run 'n' Gun.  With a bit of help from Up Close, any time you're threatened by ranged, just whip out your piece, hold the trigger and sprint at them, full bore and screaming. With all the crit bonuses from talents, blessings and perks attached, it also lives up to is name beautifully. Everything gets shredded except for carapace, which is fine since that's what the entire rest of your kit is for.

Now the MAIN reason I went with shredder, before i found out about the innate run and gun ability, was because it works brilliantly with Terminus Warrant. The crusher is already amazing vs everything not immune to stagger, but if you think you'll need a little extra oomph, either before or mid fight, dropping back for a second and mag dumping with the shredder will immediately bring you up to full power. 

Now, you might be thinking Forceful would synergies with this build more, and... well, you're not incorrect, especially with some of its modifier nodes, but between the Indignatus Mk IVe Crusher, Break the Line and Arbites Grenade, you're not lacking for stagger, and for keeping everything staggered. 

End of the day, this is a flavour build, not a meta one, though I do have regular, highly entertaining success with it in auric maelstrom. And like most recipes, you can change many things about it to make it better, more viable, or just more suited to your palette. The only core ingredients to this specific recipe are the crusher, the shredder pistol (with associated blessings/nodes in 3rd paragraph), Lone Wolf and the grenade. Break the Line is the gluten of the dish, usually necessary but if you're allergic, can easily do without. Terminus Warrant is encouraged but not a staple, everything else is up to you. 

Oh, and curios... idk mate whatever you find works best.