One of the lastest adquisitions Ive got its: "The Screenused Retractable Dagger" used by Lucy Lawless in the episode "Mortal Beloved" to kill Marcus when they were in the underworld to return the helmet of invisibility to Hades.
The dagger blade is made out of heavy metal and the handle and leather wrapped are resin. Also, the blade is retractable, that was the kind of special effects from the 90's. However, it's in very good condition for have been used in 1995. I've adquired this dagger from a collector that bought a large batch of props in the Turners Auction in New Zealand in 2001, and it has been stored since then.
Here is Lucy Lawless holding the dagger after killing Marcus in front of Hades.
This kind of metal props and retractable daggers and swords used to be wielded by main characters, like Lucy Lawless, and for scenes with short and detailed shots or close-ups.
In my opinion, the screenused daggers are one of the more demanded props used in the tv show that every xenite could have one at least.