I agree with the Dark Self pick. On a similar note, I like bosses that have a similar skill set to you or feel balanced. I like it when the boss does not simply have a long health bar for you to wittle down but rather is as skilled as you at defending/dodging/etc. Also, variety is important. I like boss fights to develop as the fight progresses. I like the idea that the boss is getting more desperate as you continue to pummel them. Good blog by the way