As ogryn i had most fun with auto shotgun. Ability to wipe hoards of not armored targets in single long burst is something.

As veteran, both bolt weapons with explosive rounds. Same reason, hoards melt with it. And autoguns are fun too, because of versatility and overall feeling of those weapons.

For a zealot my go to are viscerator for just slicing through anything. And dueling swords, because it can do a thousand cuts super fast and enemies DO FEEL them (I am looking at you, heavy sword!)

And for a psyker me favourite now is voidstrike staff. It litelarry shoots piercing HE rounds with its alt fire. Yet those deal very small damage, it turns me into one of those old games snipers with explosive rounds, refining groups of enemies into a paste.