One that I used
on AlternateHistory.com (in the form of a Double-Blind What-If, meaning the participants pretend to be characters in the universe created by the divergence) was that the Tunguska meteor hit Paris, instead of Tunguska, and the knock-on effects of that, such as the formation of an International Asteroid Tracking Service, an early craze for 'scientifiction', and a retreat from Metropolitan France to the colonies.