Cool topic! I like many you've mentioned, but my favorite weapons of all-time come from A Land Fit for Heroes. And its not til the final book The Dark Defiles, that they get that special touch.
Archeth, who is half human/Kiriath, has an assortment of Kiriath steel daggers (sharpest product in the world, duh). Long story short, she meets a Warhelm (a machine made by her fathers race used for......war!) and is trained how to properly use them. They are essentially an extension of herself, and when she needs them they will "jump" out of their holders and into her hands. Totally awesome and the names are too. Bandgleam, Quarterless, Laughing Girl, Wraithslayer and Falling Angel. And Ringil's sword Ravensfriend (also Kiriath steel), isn't too shabby either.