As Where iam Sure this Would be nonthing short of Awsome and impressive with abit of Fear Iam Not one who is a fan of the Mortal Gaurdsmen XD
Lightning Claws, Meltaguns, and Plasma weaponry all immediately come to mind. Especially plasma, it's good against everything.
Autocannon. Sweet range, packs a devastatingly heavy punch, and has a surprisingly high rate of fire for a heavy weapon. Not as high a rate of fire as the heavy-bolter, not as at armour hunting as a lascannon or multi-melta. But like the missile launcher (my fall choice in the heavy weapons department) it's fairly versatile and can out distance a lot of stuff (like return fire )
It matters not from whence the blood flows. Except by sorcery, that is a mockery to the Great Khorne.
Agreed on the autocannon. Better to take a solid, reliable and versatile weapon until you know what the battlefield looks like. The versatility of the missile launcher is great as well with its different munitions (the abysmal accuracy of the missile launcher on infantry targets made me hate the thing in the DoW games though). But I will probably be that jerk using a lascannon in a manner other than intended, looking for enemy hero classes, TDA and equivalent units and people that look important or spawned in with expensive looking equipment. Loyalists are pretty good about making themselves look real important, so it's easy to pick out who to shoot first.
Take into consideration the enemy we are most likely going to encounter. Nids. Preference for me would have to be a Heavy Flamer or Heavy Bolter. For melee, Paired Lightening Claws or Chain Sword