From About.com's Classical History page, about the Olympics, "cheaters" version
Cheating During the Ancient Olympics
Instances of Bribery and Cheating at the Ancient Olympics
By N.S. Gill, About.com
Cheating seems to have been rare at the ancient Olympics, which traditionally started in 776 B.C. and were held every 4 years thereafter. It is assumed there were cheaters in addition to the known ones listed below, but the judges, Hellanodikai, were considered honest, and on the whole, so were the athletes, -- partly deterred by stiff fines and the possibility of flogging.
This list is based on zane-statue witness Pausanias, but comes directly from the following article: "Crime and Punishment in Greek Athletics," by Clarence A. Forbes. The Classical Journal, Vol. 47, No. 5, (Feb., 1952), pp. 169-203.
1. Gelo of Syracuse
"Winner of a Roman Chariot Race"PD Courtesy of Wikipedia
Gelo of Gela won an Olympic victory, in 488, for the chariot. Astylus of Croton won for the the stade and diaulos races. When Gelo became tyrant of Syracuse -- as happened more than once to the much adored and honored Olympic victors -- in 485, he persuaded Astylus to run for his city. Bribery is assumed. The angry people of Croton tore down Astylus' Olympic statue and seized his house.
2. Lichas of Sparta
In 420, the Spartans were excluded from participation, but a Spartan named Lichas entered his chariot horses as Thebans. When the team won, Lichas ran onto the field. The Hellanodikai sent attendants to flog him as punishment.
3. Eupolus of Thessaly
"Bases of Zanes"Public Domain. Courtesy of NeilEvans at Wikipedia.
During the 98th Olympics, in 388 B.C. a boxer named Eupolus bribed his 3 opponents to let him win. The Hellanodikai fined all four men. The fines paid for a row of bronze statues of Zeus with inscriptions explaining what had happened. These 6 bronze statues were the first of the zanes.
4. Dionysius of Syracuse
"Boxers, one with blood, by the Nikosthenes painter. Attic Black-Figure Amphora, ca. 520-510 B.C."Pankration Research Institute
When Dionysius became tyrant of Syracuse, he tried to persuade the father of Antipater, the boys' class winning boxer, to claim his city as Syracuse. Antipater's Milesian father refused. Dionysius had more success claiming a later Olympic victory in 384 (99th Olympics). Dicon of Caulonia legitimately claimed Syracuse as his city when he won the stade race. It was legitimate because Dionysius had conquered Caulonia.
5. Ephesus and Sotades of Crete
In the 100th Olympics, Ephesus bribed a Cretan athlete, Sotades, to claim Ephesus as his city when he won the long race. Sotades was exiled by Crete.
6. The Hellanodikai
The Hellanodikai were considered honest, but there were exceptions. They were required to be citizens of Elis and in 396, when they judged a stade race, two of the three voted for Eupolemus of Elis, while the other voted for Leon of Ambracia. When Leon appealed the decision to the Olympic Council, the two partisan Hellanodikai were fined, but Eupolemus maintained the victory.
There were other officials who may have been corrupt. Plutarch suggests umpires (brabeutai) sometimes awarded crowns incorrectly.
7. Callippus of Athens
In 332 B.C., during the 112th Olympics, Callipus of Athens, a pentathlete, bribed his competitors. Again, the Hellanodikai found out and fined all offenders. Athens sent an orator to try to persuade Elis to remit the fine. Unsuccessful, the Athenians refused to pay and withdrew from the Olympics. It took the Delphic Oracle to persuade Athens to pay. A second group of 6 bronze zane statues of Zeus were erected from the fines.
8. Eudelus and Philostratus of Rhodes
"2 Youths Wrestling and Trainers. Drinking cup (kylix), by Onesimos, c. 490-480 B.C. Red-Figure."Pankration Research Institute
In 68 B.C., during the 178th Olympics, Eudelus paid a Rhodian to let him win a preliminary wrestling competition. Found out, both men and the city of Rhodes paid a fine, and so there were two more zane statues.
9. Fathers of Polyctor of Elis and Sosander of Smyrna
In 12 B.C. two more zanes were built at the expense of fathers of wrestlers from Elis and Smyrna.
10. Didas and Sarapammon From the Arsinoite Nome
Boxers from Egypt paid for zanes built in A.D. 125.