Stung by the embarrassment of having a number of CIA assassination operations made public, President Ford responded by signing Executive Order 11905 on February 19, 1976. The order reformed much of the intelligence community in the US, ensuring greater oversight and civilian control. It also explicitly banned political assassination as a form of espionage or regime change.
President Carter signed additional executive orders that strengthened Ford's reforms, though it'sdebatable as to what effect, if any, they had in reeling in the abuses of the CIA. It was also possibly made defunct by President Bush's signing of the Authorization of the Use of Military Force Against Terrorists in the wake of the 9/11 attacks.
Signed by the second President Bush on November 1, 2001, Executive Order 13233 caused enormous controversy for restricting access to presidential records. Previously signed executive orders called for presidential papers to be made available to the public 12 years after the term of a president ended. With President Reagan's papers about to be made public, Bush delayed their opening until he finally signed the order.
While this would seem to be a reaction to the 9/11 attacks, Bush had been postponing the release of Reagan's papers since shortly after he took office. The order stood for his entire presidency, until it was abolished by another executive order, this one signed by Barack Obama the day after his inauguration. Notably, the new executive order also makes the vice-president's papers public, which the previous order didn't.
By signing Executive Order 12148 on on July 20, 1979, Jimmy Carter kicked off the stuff of a thousand conspiracy theories. Authorizing the transfer of duties to the newly created Federal Emergency Management Agency (FEMA), the order was deemed necessary to combine disaster preparedness agencies spread across the entire federal government, putting it under the control of one director who wouldn't be hamstrung by administrative blocks or conflicting rules.
Meanwhile, conspiracy theories abound regarding FEMA using a network of secret camps to imprison US citizens in preparation for martial law and the presidential abolishment of freedom. None of this is included in the executive order.
With the Civil War raging, President Lincoln took a drastic and controversial step to sign an executive order that suspended habeas corpus, the right of the accused to report unlawful detention. This was done in the guise of Commander in Chief, to stop a Southern-sympathizing legislator from blocking the movement of Union troops to Washington, which was virtually undefended at the start of the war. While the initial order only allowed for warrant-less arrest between New York City and Washington, two years later, a Congressional act expanded it to the entire country. The Union army now had the right to arrested almost anyone without a warrant, and imprison them without a trial. The Chief Justice of the Supreme Court declared Lincoln had no military right to suspend habeas corpus, but Lincoln persisted. The suspension was only overturned five years later, when SCOTUS ruled that civilians were not subject to military law.