Lifthrasil: All of history is fascinating. But the period that interests me most are the crusades. Especially the 3rd crusade, I.e. the time of Barbarossa, Richard Lionheart and Sultan Saladin. You get several dominant historical figures at once and the events of that period have a deep impact on everything that follows after.
My second pet-period is the 1920-es. A very interesting period torn between hope and fear. Everything was changing, science, art and society. Everything was new. But also the political scenery was changing daily and dangerously so. So it's a very vivid period with lots of things to study.
Apart from these two I am also very interested in early-historic cultures like Babylon and Sumer. First appearance of script, fist recorded mathematics and astronomy and one of the first transitions from a rural to an urban society.
Don't forget Sumeria is where the first recorded religion is found, as well. It's the religion that a certain book is supposedly based on.
It's kind of creepy to think the first recorded religion of humanity was an evil one, and begs the question of whether humanity is born evil, or becomes that way.
Back on track, my favorite historical period was Ancient Greece during the heyday of Greek mythology. Something about the Greeks, and their take on gods being utterly humanistic really grabs me and dances.