What are the best (most damage) weapons for each of the characters in the original Final Fantasy?
These answers assume vanilla/classic original Final Fantasy. I've honestly never played any of the ports/reissues to know what's availiable in the bonus content or if anything has changed
Black Belt/Master: Bare Hands
Everyone Else: Masamune
Sadly, you only get one Masamune, so give the Masamune to your White or Red Mage/Wizard, and for the rest, use these 'Second Best' options, listed roughly in order of 'who not to give a Masamune to' if someone else in the party can use it, from least deserving (has the best alternative) to most.
Black Mage/Wizard: Cat Claw
White Mage/Wizard: Thor's Hammer
Red Mage/Wizard: Defense Sword
This website has a chart of weapons and which characters can equip them. The Masamune has the highest attack stat (56) and can be equipped by all characters, so I would assume it's the strongest.
The Xcalbrer is the second strongest weapon with an attack stat of 45, and can only be equipped by Knights. The Katana has an attack stat of 33 and can be equipped by Ninjas.