In terms of human history (~2M years or so), I'd have to say the Enlightenment is extremely interesting to me. I really only know the basics of the Enlightenment, and that's just the tip of the iceberg there. All the new schools of thought and philosophical revelations are just so fascinating to me.
Also, World War One is by far the most interesting event to have occurred during the 20th century, to me at least. The fact that it was a springboard for new types of warfare and weaponry (poison gas, shell-fire, trenches, tanks, etc.) really sets it apart from every other war that has taken place before and after it. WWI is a subject that I'm fairly knowledgeable in, having written 2 academic papers on topics to do with the war - one on life in the trenches and the other on the Battle of Vimy Ridge.
Now, in terms of history before the existence of humans, dinosaurs are interesting to me as well, but I don't know enough about them
