Hippos Akontistes (literally "cavalry javelineer") is the standard among Hellenic light cavalry. Hippakontistai are lightly armored, often wearing nothing but padded cloth for protection. The key to their method of warfare is speed, and they are armed accordingly. They ride small, but swift horses and harass enemy infantry and heavy cavalry with javelins. This is their primary use, because their light armor is really a detriment when they are engaged in any kind of melee combat. Their swords and shields are simply no counter to lances or heavier cavalry swords.
Historically, Hellas did not have a great tradition of light cavalry warfare, or indeed of any cavalry warfare. Hippakontistai were much like the Equites of Rome, the spoiled children of the richest families that could afford horses. They were usually not used in any front line capacity other than skirmishing and pursuit, and their equipment reflects this. Makedonian cavalry of the same type operates in a similar fashion, but generally comes from the poorest noble families, those who can afford horses but not the heavy armor required for the heavy cavalry.
These cavalrymen are best used for harassment, killing elephants from a distance, and catching routers. Although they carry armour-piercing swords, they won't last long in melee against other cavalry or infantry, so their use in close combat is very limited.
They are the only native light cavalry available to most Hellenic factions, and quite important in campaign, being available from tier 1 MICs and having a very large AoR.