If You Could Change Any Historcial Event, What Would You Change?

[Qin Shi Huangdi]

Similar to "Which historical figure would you kill" thread.

The only real rules are:
-No changing religious events (ie say preventing the Crucifixion for example)
-Be serious (ie no "John Doe eats Cheerie-Os instead of Corn Flakes on the morning of June 1st 2005)

-The Union decisively wins the Battle of Chancellorsville, ending the Civil War two years early (while the Emancipation Proclamation still takes place)
-The British and the French launch an offensive against Germany while most of the Wehrmacht is in Poland is in 1939
-Richard Nixon is elected President of the United States in 1960