The basic Magnet Warriors are all Normal monsters. Even tho you might want them in your graveyard to use the effect of Delta The Magnet Warrior, you can also use Dark Factory of Mass Production to retrieve your Magnet Warriors and use them to special summon Valkyrion the Magna Warrior.
Gem-Knights do a lot of fusion summoning so they can quickly deplete their hand. Use Dark Factory of Mass Production to retrieve Gem-Knights from your graveyard that you can use for more Fusion summons.
There are some powerful Normal monsters with lots of support you can retrieve with Dark Factory of Mass Production. If you retrieve a high-leveled monster this way you can use Ancient Rules to special summon them from your hand. You can also retrieve a high-leveled Normal monster and discard it to special summon Cosmo Brain.