There are many fist weapons, actually. One for each ore type, pretty much. There's also several others in addition to that. That's plenty for the least used weapon type in the game.

https://github.com/sayterdarkwynd/FrackinUniverse/tree/master/items/active/weapons/fist

the above lists each one we have.

Well, on the Armor and Weapons tree of the research, then you unlock block with new weapons, there are many sets that do not have fist weapons. As for the least used weapons in the game, I'm only using them because daggers got nerfed and their knockback was given to fists, I guess.

After Iron Fist, it's a while before you see another.