The only one I know of is Torian Kell's Ancestoral Sword, and I don't think there is anyway to return to Arcanum, unless somebody makes a sequal inwhich you can use your characters that are fromt he original, with equipment and all.
All weapons n such have a specific ID number. I've been trying to find out that sword's ID number so I can make a background start out with it...
If you figure out how... I hope we see it here. I'd love to play a loser that stumbles onto something way more powerful than they should have. Kinda like mankind and the bomb. ; )
After the game end, someone said about a bug not seeing the narrator but got to talk to other characters.