Talos

In the Cretan tales incorporated into Greek mythology, Talos (Greek Τάλως; Latin Talus) or Tálon (Greek Τάλων) was a giant made of bronze (an automaton made by Hephaestus) who protected Europa in Crete, circling the island's shores three times daily while guarding it and throwing stones at any approaching ship to protect the island.

Mythology
When Jason (Argonaut) and the Argonauts approached the island of Crete, for the golden fleece. As the guardian of the island, Talos kept the Argo at bay by hearling great boulders at it. Medea, the sorceress, either drove him mad with drugs, or fooled him into believing that she could make him immortal by removing the nail and killed him with the same nail.

The Titan's Curse
Percy, Thalia, Grover, and Bianca di Angelo fight a malfunctioning prototype of Talos (That Zoe says is smaller than the original) in the Junkyard of the Gods. Apparently, he has a manhole at the base of his foot for 'servicing'. Bianca enters the hole to haywire his circuits so that they could defeat him. He fell on some power lines that electrocuted Bianca.

Trivia

 * Talos is the only enemy Percy faces in the series that is not a monster, god, or human besides Festus.