Erik, I don't know if this was intentional, but I discovered a really simple counter triangle on the game! Kind of like Rock-Paper-Scissors, and here it is:
^Bow < Sword
I can explain in more detail:
The hammer is (on paper, because it sometimes takes a single voxel off. >:( ) the most powerful weapon on the game, with a huge PTK (Potential To Kill), capable of dealing a powerful, unblockable strike, which deals considerable damage and is almost guaranteed to kill a robot in one hit, however, despite this, a skilled bow user AKA MK3 Combat Flipping Campers can easily dispatch a hammer wielder, because of the inability to block arrows.
The sword is the game's starter, and most basic weapon at the moment, it has two main special abilities, other than, obviously, chopping robots in pieces, it can be imbued with a fire effect, which increases its PTK reasonably, the other ability is to block arrows, thus, succesfully countering most archers, the MK3 variant of the Sword Robots has this ability, thus making them almost impossible to kill with a bow, it's also the only weapon that can block any attack except for hammer strikes.
In my opinion, the weakest weapon in the game, with a low PTK, and slow moving projectiles, it may be just because of my total inability to shoot a ranged weapon that isn't a gun in most games, and, for some reason, the archers are the most annoying enemies in the entire game... ugh, but, anyways, it's true power shines in taking down hammer wielders, as they can't block arrows, unless they dodge, which is extremely improbable, as their movement is rather slow, and they are really BIG, but this weapon can be easily countered by the sword with the block arrows upgrade.