Shield emblem of the Spartan mora - Copyrighted image courtesy of Nikos Panos & George Heliopoulos
'The 300 Spartans' (c) 20th Century Fox
Since all Spartan males served in the military, there was no higher honor than to be a part of the elite unit known as the 'Hippeis', who were the King of Sparta's personal bodyguard. This unit was comprised of the 300 best Spartiati warriors who were held in the highest esteem by their fellow citizens in Sparta. These hoplites stood shield-to-shield protecting their king in the phalanx formation alongside with their countrymen.
The Hippeis usually consisted of Spartans who were in their early to late twenties in age. However, King Leonidas ordered that only men with living sons would accompany him to Thermopylae, thereby guaranteeing that the Spartan hoplite's bloodline would not extinguish with his death on the battlefield. However, it is highly improbable that all of these elite warriors had produced a male heir.
Consequently, it can be concluded that the 300 Spartiates who fought at Thermopylae in 480 B.C. were comprised of a combination of Hippeis and battle hardened veterans.
In one of the passages from Book 7, Herodotus wrote that he had seen the names inscribed on a pillar in Sparta of the Spartiates who fought and died with King Leonidas at Thermopylae. Pausanias who was a traveler, writer and geographer claimed to have also seen the memorial in the 2nd century A.D. He is not to be confused with the general and regent Pausanias who led the Spartans at the Battle of Plataea, nor the Spartan king (409-394 B.C) of the same name.
Unfortunately, the pillar doesn't exist any longer, destroyed by the ravages of time or perhaps some natural calamity. Therefore, the only names that exist are the few mentioned by Herodotus (see below).
Dienekes (Dieneces) - Herodotus wrote that he was the bravest of the 300 and who was immortalized by not only his deeds, but the following: When told that "The Persians were so numerous that their arrows would blot out the sun", his reply was "Good, then we shall fight them in the shade!" As a testament to Dienekes Spartan wit, Richard Egan as King Leonidas in 1962's 'The 300 Spartans' spoke this line as did Michael Fassbender who portrayed Stelios in Warner Bros. '300'.
Maron and Alpheus - Two Spartan brothers who also distinguished themselves and possessed that quality known as andreia, which in Greek means courage and bravery.
Pantites - Sent away from Thermopylae on a diplomatic mission to enlist the services of the other Greek city-states. He later hanged himself because of the shame and the dishonor bestowed upon him by his fellow Spartans who thought he had loitered long enough not to engage in battle.
Eurytus - Suffered a very severe eye inflammation which incapicatated him so much that he ordered his helot to guide him into battle and perished with the remaining Spartans on the final day.
Aristodemus (Aristodamus) - Suffered the same inflammation as Eurytus, however, instead of fighting, returned back to Sparta and was labeled 'The Trembler' for not having fought and died with his fellow Spartans. Aristodemus' redemption came when he stood in the front line of the phalanx at the Battle of Plataea, broke ranks and killed several Persians on his own before dying.