Owen's Knife Zealot
 Zealot Build - Warhammer 40k: Darktide 

Purpose of the build is to tank frontline and crit as often as possible to refresh Chorus. The toughness damage reduction you're getting should allow you to survive basically any horde or damage source as long as you're moving around and using dodges to regenerate toughness (Second Wind is crucial, as your primary toughness regenerator outside of coherency). If things get hairy, you can easily sprint out with the knife and play for survival, at which point the build has excellent attrition survivability as long as you're hitting dodges. 

If you have Chorus, and there aren't zero enemies around, pop it and give your team the toughness reduction (40+15aura) for 10 seconds. You should be using the light attacks of the knife to get more crits, to reduce cooldown, to pop it again within 20. As long as you're dodging, you basically don't take damage.

Shotgun should be used primarily for guaranteed kills at medium range on specialists and for fending off waves of ragers. Killing dogs is somewhat difficult due to the low range of the knife and the low capacity of the shotgun, so be on the lookout for those. 

note: Curios don't matter those are personal preference !