Akontistai advance at speed to pepper an enemy with javelins, and then withdraw in good order before a counter-attack can be organized.
Those unlucky enough to be extremely poor freedmen were pressed into service as psiloi, missile units, and the lowest class of Hellenic infantry. The Psiloi were divided into three parts: javelineers, slingers, and archers. The javelin-armed Psiloi, the Akonistai, were ragged peasants armed with javelins and small knives. Their function was simply to throw their missiles and then run as fast as possible to safety behind the Hoplitai lines. They were used for skirmishing and to provide a demoralizing hail of missile fire during the grinding battle between the two phalanxes. Never use Akonistai in melee except as diversionary fodder or as a flanking force; roles in which they don’t excel, but might actually be better than nothing. They have their uses, as their javelins are still sharp and deadly, but they were often used only as light skirmishers or as a last resort in Hellenic armies for obvious reasons.
Historically, Akontistai did not play a particularly large role on the battlefield, and weren’t normally a particularly decisive force. They were used mainly for their ability to induce an enemy to attack prematurely. They are little more than an annoyance on the open field, but can be deadly if positioned in places where their javelins can be used for maximum effect: on high terrain, on an enemy unit’s flank, or atop a city wall.
The Akontistai, when used correctly, can be dangerous assets to any Hellenic army. Being cheap and having a wide AoR (Area of Recruitment) means they can be spammed and used as "suicide units". Suicide units are units that a player uses for the sole purpose of either luring the enemy into a trap, diverging the attention of the enemy away from the main battle line and providing the rest of your units with cover against missile fire. All of these usually result in the "suicide unit" sustaining severe casualties or even routing in the process.
Apart from suicide missions, Akontistai can also be used as traditional skirmishers. This means peppering the enemy with javelins before the main engagement in order to thin out the enemy lines, followed by a quick retreat to safety. In that sense, it is wise to keep Akontistai in Guard and Skirmish Mode, the former to ensure they will not be forced into combat with an engaging enemy unit and the latter to have them automatically run away from approaching enemies. Their great numbers means many javelins, and so even after initial skirmishes there are usually some volleys left that can be used in the course of the battle for many purposes. Furthermore, they can also be used to eliminate strong enemy missile units. Missile units like the Toxotai Kretikoi and Sphendonetai Rhodioi can be a serious threat when used properly (usually the case, even with AI control), mainly because they have very long range and can eliminate entire cavalry or light infantry/missile units if left unchecked. In case of an encounter with such units, the utilization of a few Akontistai units is ideal as they a) attract enemy missile fire when placed in front of the army, and b) are very effective against lightly-armoured units thanks to their javelins.
Javelins are especially deadly when fired from elevated terrain towards an approaching enemy, so placing the Akontistai on high ground or on top of city walls will deliver extra damage to the enemy. Also, firing a couple of javelin volleys at the exposed backs of enemy units that are engaged in combat is usually sufficient to cause a rout. That, coupled with their intrinsic mobility, makes them suitable for flanking maneuvers as well, provided there is no cavalry or infantry to do the job instead.
Even so, Akontistai remain ill-armoured and undisciplined, and as such should avoid direct combat with even the lightest of infantry units. Cavalry should also be watched out for, and so in order to provide the Akontistai with protection it is a wise idea to keep mobile light or medium infantry like the Hoplitai Haploi and Thureophoroi closeby. Cavalry like Hippeis and Prodromoi can also accompany Akontistai in order to make sure enemy cavalry do not attempt to engage them.
Below is a picture showing the AoR of the Akontistai: