>>2013535
i think the "other weapons" might just be for weapons that you can't start the game with. there isn't anything special to them otherwise though, and i think they all share skill trees with other weapons that you CAN start with (i.e. the skill tree for regular swords also includes skills for 2H swords).
getting them is just a matter of buying/crafting/finding them like you would any other weapon.
dunno about the knuckles, haven't tried them yet.
also that page doesn't mention it, but there's also a skill tree for being completely unarmed, though unlike the other weapons you (technically) can't start with it. you get the level 1 skill tree for whatever weapon you start with, but you have to pay money to unlock other skill trees, including unarmed.