44BC. Julius Caesar was assassinated in the Senate House by a group of senators led by Marcus Junius Brutus and Gaius Cassius Longinus. He was stabbed to death on the floor of the senate, and according to Shakespeare his final words were "Et tu, Brute." ("You too, Brutus"). It was not of course the first time Brutus had betrayed him, having fought against him in the civil war (and been pardoned and welcomed back into the fold by his old friend Caesar).
The miurder of Caesar was ostensibly to restore the republic of Rome, but instead plunged it into yet aother civil war and produced the first Emperor - Octavian, Caesar's adopted heir.
Also on this day:
1493 - Columbus returns to Spain from his voyage that discovered the Americas.
1869 - The first ever professional baseball team, the Cincinatti Red Stockings, played their first game
1877 - The first Test Match took place, between Ausralia and England. Australia won by 45 runs.
1917 - Nicholas II , last Tsar of Russia, abdicated
1937 - The first ever Blood Bank was set up in Cook County Hospital, Chicago
1990 - Farzad Bazoft, British-based journalist for the Observer was executed in Iraq

Of course that wouldn't be as
fun.