I'm working on a modded version of the Necklace Of Unlocked Possibilities which will summon any weapon in the game including the DLC, but I don't know if the pre-order weapons are included in the game code. If they are then I could add them to the list of weapons the necklace summons, if not then it'd mess the whole thing up because only people who pre-ordered the game would be able to see the modded item. I'm also not entirely sure which weapons were pre-order bonuses. There's the Drogga's Skull sabre and the Matakau axe. Any others? And are the items available at all to people who didn't pre-order?

Hmm, Defiant Apparel hat? (Perception resistance)

St. Drogga's Skull is the only weapon you get from just the pre-order bonus, as shown here. I'm not sure what the Matakau axe is.