Iraklis (Hercules): His mother Alkmini was seduced by Zeus who took the form of her husband to sleep with her. Hera\'s wrath for Hercules is well-known, as she even sent two big snakes to his crib as a baby to kill him. Hercules killed them, but this wouldn\'t be the last of his achievements. As obedience to the oracle of Delphi, he had to perform 12 major labors (killing the Lernea Idra, taking the hide of the Nemean Lion etc), which made him famous.
Alexander (the Great): The famous hero\'s mother Olympia, a queen of Macedonia, claimed that Zeus himself had fathered her son.
Athena: The goddess of knowledge and war sprung out of Zeus\'s head. Zeus laid with her mother Metis, the wisest woman in the world, and fearing that Metis might give birth to a child stronger than Zeus, he swallowed her and when it was time for Athena to be born, Zeus asked for Iphaistos to crack his head open, because he had a horrible headache. Athena jumped out in full armor as she is depicted in paintings.
Apollo and Artemis: The mother of these two Olympian gods was Lyto, a titan. When it was time to give birth, Hera pursued her relentlessly so that Lyto wouldn\'t find a place to give birth to her children. The island of Dilos, hidden from the sun, provided her with refuge where the two gods were born. Artemis was born first, helping her mother give birth to her brother Apollo.
Dionisos: The demi-god of wine and fun was born out of Zeus\'s thigh. Semele his mother was seduced by Zeus, but when Hera found out, the goddess tricked her into getting struck by Zeus\'s powerful lightning bolts. After her death, Zeus rescued the baby, keeping it in his thigh until it would be ready to be born.
Ermis: One of the 12 Olympian gods, Ermis was the offspring of Zeus\'s union with a nymph named Maia.
Perseas: Hercules is actually a descendant of Perseas. Perseas\'s mother, Danae, was impregnated by Zeus when he took the form of a golden shower to reach her in a bronze cell, where her father had locked her in hope that she would never bear any children (the oracle had told Danae\'s father that his grandson would eventually kill him). When her father found out she was pregnant, he threw her and the baby Perseas into the sea in a golden chest and the baby survived, eventually killing his grandfather, accidentally many years later.
Minos, Sarpedon, Rhadamantes: Their mother Europa (it\'s where we get the name for the continent Europe) was a princess in Phoenicia who was abducted by Zeus in the form of a bull, bringing her the whole way over to Crete.
Read about the rest of the "bastards" at allthegreeks.com
Source: theoi.com
Image: Zeus and Europa by Alexandru Radvan http://radvanpainting.blogspot.com/2007/04/zeus-and-europa.html