Are we discussing maces and their effective use as it pertains to cavalry or simply in general? It would seem that the effective usage of maces in combat were usually on horseback, the speed of the horse allowed the accumulation of force that when making contact with armor caused heavy blunt trauma. This makes sense for cavalry, especially heavy armored ones, yet for infantry it does not or for enemies who are more lightly armored and can avoid the blow more easily than someone covered in armor. Swords and other weapons are at least have typically better ranges and are better when enemies are no longer at a gallop and battle in a position of stagnant combat. If I am correct too, the first usage of maces on horseback that was notable, was their usage among the cataphracts and other heavily armored cavalry of the Arsacid period. If this is so, it should be remembered that prior to this, the primary horseback weapon used were three, bows, javelins and lances/spears (with a shield). What this informs us, is that the initial fear of cavalry was that due to armor restrictions, they would not be able to get close enough to use a mace or sword at a level more efficient than an unmounted foe; hence the lance and its use to keep the enemy at length and yet gain from the speed of a horse and its kinetic power. Bows and javelin, likewise, were good in that they allowed with a level of practice, the ability to have a more mobile and versatile skirmisher. So, the only reason maces made the move to cavalry from infantry (as what seems, in ancient times, a weapon used to acquire slaves) was that due to increased armor of Arsacid-Scythian-Sarmatian cavalry, the horseman could get closer to his enemy without fear and thus accumulate that famed blunt trauma blow to an armored enemy.
Maces are also not created equally... Some maces and blunt weapons were used along with other weapons such as nooses, clubs, bolas and whips to subdue enemies lacking armor and to capture loot in the form of slaves/prisoners. Imagine the better usage of maces in this instance, as weapons that cause blunt damage that may not kill foes if used with intent, whereas bladed weapons could cause wounds that would be unhealed and cause rapid death if unattended or unlucky. One should remind themselves of the example of the warriors of Mesoamerica, who other than bows, bolas and obsidian blades, possessed only blunt weapons and these in their blunt weapons primarily for the capture of prisoners. These blunt weapons would have been less than satisfactory in combat with most 'old-world' armies post 900 BCE. Other peoples can be seen even today using only blunt weapons in varied ritualized warfare, such as in Papua New Guinea or in Indonesia and the jungles of Southeast Asia, where such blunt weapons are cheaper and used by footmen. This usage, one can observe and reason, is certainly generally inferior to sword usage.
Flails as was mentioned once within this thread, as is known, when used on horseback, carry the risk when facing able bodied enemies, the ability to miss and arcing around, causing potential damage to the user. Further, when not fighting lightly armored mobs or fleeing enemies, the concept of these erratic weapons, is always weaker than more orderly formations using simple and versatile weapons like spears or swords with shields. The flail, does not also seem effective at all when used by more than sections of a cavalry, the momentum gained from swinging such a weapon whilst on foot, I would imagine, is minimal and dangerous to your compatriots near you. If you are seeking a weapon that is not slashing-puncture related, yet with range, the noose is definitely a better weapon than the flail on both horse or foot for subduing heavily armored horseman or for a variety of roles. If trained in the skill, a rider for instance, with a bow/javelin and noose, could throw a noose and grasp hold of an enemy rider and pull the rider from his horse and carry him and for many warriors, dismounting meant death or capture. Nooses can also be used to disarm enemies and unnerve enemies who fear being dismounted or if infantry, being dragged a distance.
Ultimately, a mace using horseman would have his most difficult time with enemies who are lighter and use bows, nooses and swords. It is unlikely that said warrior with mace wearing heavy armor will connect with said horseman and his heavy armor becomes a nuisance, as it drains his/his horse's energy and is required to retreat or worse, is pull from his horse by a noose and once ensnared, they can take simply drag him a distance and on his rise, even a sword would could cause injury or wounds that kill. It should be remembered, that many times in the past, heavy armored horseman bearing maces were totally outdone by light cavalry bearing bows, javelins, maces and nooses. At the battle of Anzen-Danzimon, light cavalry bearing bows was able to hault the march of the entire Kurdo-Byzantine army, including the heavily armored cavalry present. On the island of Crete, Muslim pirates armored with light armor, bows, javelin and such, bested maces-heavy armored cataphracts (form Byzantium) simply by avoiding close combat and skirmishing and forcing the enemy to retreat due to exhaustion.
To be clear, the only time that maces were used at its most effective sense that we mentioned, as blunt trauma damage to armored enemy, was when paired to a heavily armored warrior who through their armor, could afford to get near an enemy to deliver that blow. If a lightly armored fighter uses a mace in opposition to a sword, they come to find weakness, in that the sword is usually with greater ranges and more versatile, with its myriad of ways to cause wounds and harder to avoid or block.
@phx1138 How would a yo-yo be used as a weapon? Perhaps, some sort of chain or rope with a certain ball attached, that could be rolled around each other and manipulated like some sort of blunt whip?