If you have several PODs for one century, then number them, so we can see which you find most interesting.
One for each? Damn, that's though, I'll try my best (most of them in ancient history are for the sake of completion).
900 BC - The alliance of 12 kings stop the Assyrian expansion.
800 BC - Curb the Etruscan rise.
700 BC - The Neo-Assyrian Empire survives (yeah, contradicts the first one).
600 BC - No babylonian captivity.
500 BC - Athens win the Peloponnesian War.
400 BC - Alex the Big never becomes big.
300 BC - Someone else unfies China.
200 BC - If possible prevent the Mauryan collapse.
100 BC - Reinvigorate the Roman Republic.
0 AD - No Jewish Wars.
100 AD - No Commodus or a "nicer" collapse of the Han dynasty.
200 AD - Rome-screw.
300 AD - Different Council of Nicea.
400 AD - No Angle invasion of Britannia (or it is repelled).
500 AD - No Gothic Wars.
600 AD - No Islamic Conquest of Persia.
700 AD - The Caliphate expands even more in India.
800 AD - Mercia becomes the dominant Anglo-Saxon power.
900 AD - Otto II, Holy Roman Emperor, wins the Battle of Stilo.
1000 AD - No Norman conquest.
1100 AD - Henry VI, HRE, doesn't die young.
1200 AD - Charles of Anjou never sets foot in Sicily (preferably gets killed).
1300 AD - Go-Daigo is less radical and the Kemmu Restoration in Japan lives on.
1400 AD - #YorkForever
1500 AD - A different Charles V (or Philip II) deals with the Reformation better.
1600 AD - Imperial victory in the Thirty Years War. :^)
1700 AD - No rise of Prussia.
1800 AD - Qing China and the Ottoman Empire are more successful.
1900 AD - Jesus, there is a lot, the most basic is no WWII of some kind.
2000 AD - No 9/11.