Can you name some powerful weapons in Greek Myths for me please?

Trident is a weapon of Poseidon, lightning is Zeus' weapon. You can find list of ancient weapons link

Katoptris was a ceremonial knife that Helen of Troy got for her wedding. Odds are it never saw battle, she used it more as a miror, hence, the name.
Achilles got special armor from Hephaestus, which of course failed to cover the ankle (?)
Heracles' (Hercules', I'm sorry I refuse to use the Latin name) favorite weapon was a club, so it's safe to guess that he had a favorite club he carried around.
Perseus got an adamantine sword from Zeus to kill the gorgons.

Golden coin, I get it :P RR ahs said that the coin was a product of his own imagination and not of the myths.

Perseas got an invisbility helmet and flying sandels from Hermes and a polished sheild from Athena too.