When I re-enlisted in the Army in 2007, I saw several soldiers with Μολων Λαβε tattoos and Μολων Λαβε stickers on their pickup trucks. I can read Ancient Greek so I looked up the phrase and found it attributed to Leonidas of the Spartans, the leader of the 300 defenders of Thermopylae.
According to one version of the battle, when Xerxes, King of Persia demanded the surrender of the vastly outnumbered Spartans (100,000+ Persians against 300 Spartans), Leonidas answered "Μολων Λαβε" or "Come and take them." The phrase has come to be seen as the inspiration for the sentiment "I won't give up my guns until you pry my cold, dead hands from them."
I am currently taking a course in Ancient Greek in which we are reading the Histories of Herodotus. Right now we are reading the account of the Battle for Thermopylae. Herodotus wrote about 50 years after the battle and does not mention the exchange between Xerxes and Leonidas. I asked the professor. The only account directly mentioning Μολων Λαβε is in Plutarch written more than 500 years after the battle and centuries after Greece was conquered by Rome.
So the historicity of the account is in some question. And Sparta was a state ruled by tyranny in which the majority of the people were slaves. There was nothing like the 2nd Amendment in Sparta. If Leonidas said these words, he said them as a man who represented a warrior class, an upper class caste of warrior, nothing like armed common people. Since the only mention of the phrase is five centuries after the battle, it could well be a myth.
Leonidas would roll over in his honored grave to think his words would be used as a rallying cry for rebels and anti-government conspiracy theorists. Leonidas was the government, just as every soldier in every army, especially the "well regulated militia" our founders envisioned in the Second Amendment to the Constitution.
Μολων Λαβε, on a pickup truck next to a rebel flag means the owner of the truck is an ιδιοτης, an idiot, which means a person having his own ideas apart from his community and therefore is a fool.
For Greek Geeks: The two words in the phrase Μολων Λαβε are verbs. The aorist participle Μολων can be translated "having come or coming" and Λαβε is the imperative singular "Take."
Inflected languages can say much with few words and this phrase is a beautiful example of that. You can parse it yourself in context here.