My biggest suprise had to have been when i decided to try a new tactic as the Danes. I started a game on easy, built as many troops as i could before I ran out of money.
Then with only 100 or so florins in the vault, and about 600 guys, i attacked the HRE on a seemingly suicide run. I narrowly won the conflict in saxony, loosing about 300 men. I thought I was doomed, but as soon as I attacked, it seemed that everyone else wanted a piece of the HRE too. Within 5 turns, the HRE was at war with me, the English, French, Polish, Hungarians, and Italians. Needless to say, the HRE didn't exist by 1100.