Harry Potter could have used game theory to defeat Lord Voldemort.
No-one dared to even speak the name of Lord Voldemort, only calling him ‘He-who-must-not-be-named’, ‘You-know-who’ or ‘the Dark Lord’.
In Harry Potter and the Deathly Hallows anyone speaking his name is tracked down by Voldemort or his followers and this is how they find Harry, Ron and Hermione.
If everyone in the world had overcome their fear and spoken his name then Voldemort would not have been able to find Harry.
The author explains that having everyone collectively do the riskiest thing possible actually would have mitigated the risk entirely. Neat paradox.