I only know of a few that are seen as magical. However I'll do some research and come back to edit this answer when I find some more, but for now I'll list the ones I know.
The Armour of Achilles: Made by Hephaestus and said to be completely impenetrable.
The Helm of Darkness: Made by the Cyclops for the Lord of the Underworld Hades. It turns the wearer invisible and is said to bring out your darkest and deepest fears.
Apollo's Bow: It can cause health or famine and in some stories, death.
The Hide of the Nemean Lion: A hide worn by Hercules, or Heracles, and was able to endure every weapon and was unbreakable.