What Is The Stupidest Weapon?

Flails are actually good weapons.  The one pictured has a few problems, the chain is too long and the haft too short.  You don't need a five pound weighted end either.  A good flail is light enough to swing in a controlled motion and come up to speed without hitting yourself in the head. They are designed so the lengths of the haft and chain won't allow the flail head to crush your fingers, arm or shoulders like the one pictured.  

If that one was modeled after a museum piece I suspect it was either a theatrical prop or the equivalent of a dress/parade/bearing sword.

Well regarding that piece, "Crap" is the optimum word ! 

Well, there was the incredible Baker jumping tank. Can't tell you much about it, though. But for a stupid tank, there were proposed one-man tanks. All the little tankettes of the 1930s weren't that great an idea. Some so-called "infantry tanks" were armed only with machine guns, although some were well armored, at least. Yet, there are modern armored vehicles that are scarcely any better than the old tankettes. The automotive performance is probably better.

I can't really think of any pre-gunpowder weapons that were that stupid. Some gladiators were equipped with a net along with a trident. Modern police departments supposedly have tried out the same idea to ensnare dangerous (and presumably unarmed) suspects. The equipment includes, no doubt, a mechanism for throwing the net.

...Not sure if coat hanger or...