How do you say audacious in Japanese?.....Yamamoto
The Pearl Harbor attack was #2, IMO. Although if you count the erdication of the US, UK and Dutch navies in Asia in the first three months of WWII, Yamamoto is unrivaled.
Idiot Biden is boasting about taking out sitting duck Bin Laden, defended with small arms, when it was Bin Laden who was behind what I consider to be the most audacious and innovative and consequential single attack ever executed. The 9/11 attack was asymmetric genius in converting non-weapons (civilian aircraft) into kinetic projectiles and applying the force of those projectiles exactly in places where maximum damage could be inflicted. And the damage was simultaneously military, economic and political.
Audacious, in my mind requires complete surprise thus ruling out Normandy and others where the attack was inevitable and only the date unknown.
To rank high on historical significance the audacious attack must be consequential. This would rule out the Doolittle Raid and Benedict Arnold's slog through Maine to reach Quebec as they were not consequential.