Well, to say 'favorite', I'm not sure that I can pick just one, because every single event that has happened in the past has come together to shape the future. [And the time plane that I come from makes it different for everyone.
I've studied in particular Japanese history and culture. Such as the Edo period and Meiji era all have fascinating history, though even following the events that happened well before that, such as within the Heian period is exciting. I find even the Heisei period to be interesting. It's amazing how primitive technology was within the past. To think it has all changed so much. It's astonishing. Half of the instruments of the past, I'm not even sure exactly how they work. [I still can't come to grips with how it is that boats don't sink on the water...]