That flail is certainly the worst of the lot. Terrible impractical weapon with scant evidence of it ever being used by anyone.
There's a two-handed version of the flail that is basically an agricultural threshing tool with spikes stuck into the head, which is much more plausible as a peasant's weapon (very similar development process as the nunchaku, also a highly overrated weapon). However most weapons that feature a flexible rope/chain part in their design all suffer from the same drawbacks: difficult to control, and limited striking power.
The two-handed version of the flail is definitely real and a reasonably formidable weapon. I study at a Spanish HEMA school and we have one source—Mendoza—which basically says it should be used in the same way as the montante (the Spanish greatsword), except without thrusts. Like the montante, its best value is when against multiple opponents, such as doing crowd control or escorting someone. Mendoza also describes his flail as being made of three separate chains with individual weights on them, rather than one large thrasher-like tool as shown in the headline artwork on the Wikipedia page.
I was just saying the other day to my dad while he was watching reruns, that I wanna see the smiths making flails on Forged in Fire because it would really show their craftsmanship imo. The fact it has a chain as part of it would be an interesting challenge to watch. But mostly I wanna see Doug kill some dummies with one.
quarterstaff or bec de corbin for me. Quarterstaff can also be concealed as a walking stick, while bec de corbin gives many options (blunt weapon, armor piering spike, long poky bit)
The lack of morningstar fans is surprising. my fave is the morningstar by a lot, the sheer brutality and devastating capability against armored targets of the thing is just awesome.