Presidential executive orders have existed since George Washington used one to declare a national day of thanksgiving for the signing of the Constitution. Using powers granted by that document, laws that presidents pushed through on their own have ranged from monumental to minutiae. Many famous executive orders, like the Emancipation Proclamation or the desegregating of the armed forces, did things that Congress was unable to do, while a few were massive overreaches of power, and got slapped down by Supreme Court decisions.
In terms of President Obama, while his critics have ascribed "thousands" of executive orders to him, he's signed comparatively few in relation to other presidents. FDR signed over 3,700 orders, most related to his role as Commander in Chief in the Second World War. Presidents Wilson, Harding, and Hoover also signed hundreds per year, far more than any post-war president.
Here are some of the most surprising and important executive orders in presidential history. Not all were beneficial to the public, but all were vital to American history.
The Emancipation Proclamation
The Manhattan Project
Suspension of Habeas Corpus