I gotta go with nunchuks. Anything you sling around on a chain seems silly to me. It seems like nunchuks are only good weapons against the unarmed. Anyone else has more range, usually something sharp in play and there isn’t a limp chain in the middle reducing the force of your strikes.
For what it’s worth, if you are fighting knight vs knight, you aren’t too worried about hitting yourself with that ball&chain on the back swing etc, cuz you got good armor.
So I bet some people used it in duels and for one on one combat, but I doubt it was much of a war weapon, simply because if you are fighting next to your friends, you’d like to not hit them on accident with your weapon.