4. David Palmers Assassination
Most series of 24 end with a dramatic event but series five started with a game changer. Fans were delighted to see the return of Ex-President Palmer but then, within minutes, were devastated by his murder. The assassins bullet came as Palmer was deep in conversation with his brother, Wayne, and struck him in the throat. It was a huge shock that came from nowhere and gave no warning. It was not the first time he had been targeted (the series two finale and the entire plot of series one) but since he had since left power it seemed he had been spared. As the arcs of the plot continued to develop through the series the reasons behind the assassination were revealed, but little else that happened on day five created such a genuine shock.