Bismarck has one of the best passives if in the right situation. If you have a large map and/or few opponents, barbarians go wild and multiply like mad. Germans get 50 gold a pop at their camps as well as a 50% chance of getting the barbarian unit, so those go off and the chance for reward is exponential. I think early on, my return from gold - plus the ruin bonuses that comes with massive exploration - must have been greater than my nation's GDP. On top of that, you easily have the largest military in the game without having to build any units.