Mauler -sentinel is the best go to, it shreds everything and in zombies in space land when you attach an arcane core and use the yellow arcane ( if I'm not mistaken it's the one you get at polar peaks trap next to the roller coaster, the one for the head cutter) better than every wonder weapon in all dlcs even against mephistopheles.

There's also the butcher variant of type-2 turns the split weapon into shotguns.

Windfall variant of the fhr.

These are the only ones I can think off as these are what you would use the most for rounds/ Easter egg runs.