Decapitate Everything
 Zealot Build - Warhammer 40k: Darktide 

Hello,

I've played all 4 classes, tried many builds with them, but by far the most consistent/strongest and above all the most fun fucking build is this one. I've tested it with Blazing Piety and Martyrdom, while both keystones work very well I found that Inexorable Judgement works best for me.

1. The bread and butter of this build is the Rashad Mk II Combat Axe, while the weapon by itself is very good when you add the Brutal Momentum Blessing the weapon becomes op, you cleave through hordes, mixed hordes and elite enemies with ease. Monstrosity and Carapace damage isn't the best but still nothing to be scoffed at, hitting the weak spots will still do a lot of dmg to the monstrosities and the axe heavy attack will stagger even crushers and maulers if you hit them in the head, letting you kill them pretty easy in 3-4 hits even without using your Fury of the faithful ability, that being said everything else is fair game. For the second blessing I use Decimator because I've found on auric levels its very easy to keep the stacks high and there are so many enemies that you rarely miss with your attacks, Headtaker is also a great option - less damage but more consistent. 
2. For the ranged weapon I use the Ironhelm "Hacker" Mk IV Assault Shotgun, while perhaps not the meta choice, for my playstyle it works very well, I mainly use it to 1 shot mutants, ragers and trappers with the secondary fire, with the weapons high mobility, draw and reload speed it works very well in the heat of the battle when you need to kill a priority target that gets close to you. That being said its a close quarters weapon and you won't be killing snipers, bombers and flamers from range but that's where your knives come in, it takes time to master them but when you do, you become the sniper :D.  If you want a more reliable choice I would pick the Zarona Mk II Revolver or the Bolt gun for carapace/monstrosity damage and the ability to deal with enemies at long ranges but the revolver reload is slow and the bolt gun has a slow draw speed.
3. The curios are not set in stone, you can choose whatever suits your playstyle more, but for me, the usual zealot enjoyer who runs ahead of the team and slide spams his way into the ranged enemy ranks and murder-fucks everything that shoots your poor ogryn teammate the gunner and sniper resistance work very well because they let me make some mistakes and not get punished that hard when Until Death is on CD. 

    I hope you have fun with the build and slay many enemies of the Emperor :)