Rufus, if you think similar vs. similar is boring, I wonder why you are interested in medieval wargaming at all!
If you want battles between different kind of forces, one awesome setting would be Scandinavia during the 15th century (throw in 14th century aswell, by the way).
Farmer armies of different skill level centered around crossbows and polearms/spears, supported with some noble cavalry, maybe a sprinkle of professional foot, and a not to shabby amount of cannons against danish armies of more continental look, including many german mercenaries in horse and foot. But here to you might find a bunch of farmers who for some reason decided to join the danish king or a swedish noble allied to him, maybe because their neighbour rivals joined the other side...
Very different in capabilities, the conventional forces would usually be better on a classical battlefield, but the farmers would rule anykind of fighting in forest or broken terrain, using field fortifications, barricades and traps as well as local knowledge to their advantage if possible. And the enemy better watch out in case the farmers are supported by some swedish noble cavalry just waiting for the right moment to pounce.
But sometimes the farmers will also rather die fighting than admit defeat, and despite the odds decide to sell their lives as dearly as possible even if it means slaughter. Great examples of that would be the battle of Visby 1361, and the massacre outside Stockholm during the reign of Christian I in the mid 15th century.
But at the same time, given some time and expirience, the farmers can turn into a truly determined army with some skill to back it up. Like at the battle of Brunkeberg 1471 outside Stockholm, when the swedish farmers made 2 frontal assaults against a fortified position on a ridge, and reformed twice afterwards and went in again.
After the second (or even third) repulse, if my mind serve me right, the danish commander on the ridge belived he had finally broken the farmers and moved down to drive them of, only to see the farmers being reformed and happily engaging their enemies who had now left their good position.
