My favourite is the story that there was mass panic over a radio broadcast of War of the Worlds where everyone thought a real alien invasion was happening. I heard this story as a kid and really thought this was a cruel prank played by the radio station.
In reality, they made it clear at the beginning of the broadcast, and twice during, that it was fictional. Not that many people were listening and most of the people who were, were aware it wasn’t real. A few idiots freaked out and it somehow turned into a story of mass panic. It was propaganda by newspapers to discredit radio.
There’s a story about how Zhuge Liang, a general and strategist during the Three Kingdoms period, protected a city from a 150,000 strong enemy army by hiding his force of 100 soldiers, leaving the gates wide open and playing a lute atop them, in plain sight of the enemy general. The enemy saw that, thought “No way I’m falling for this trap” and retreated.
That never happened, but Cao Cao did pull a similar feat against Lu Bu - the town had dense forests nearby, where forces could effectively hide. Lu Bu retreated the first time, but came back the next day and attacked, only this time Cao Cao’s soldiers were actually hiding in the forest and fought Lu Bu.