I would like to see more hordes. Like… A lemming horde! There is several tiles covered in lemmings that charge across the world. If one tries to move into your square, then there is a small chance that you get knocked in the direction it travels, and a small chance of falling over. If you are knocked back then there is a larger chance of falling over. If you try to move onto one of their tiles then the same thing happens but with much greater chances. If you have fallen over then movement is guaranteed and there is a really small chance of being able to get onto your feet. So they just charge across the countryside picking up whatever is standing in their path and carrying it off to whatever, they would probably hit a river eventually and dump you into the drink, or maybe go over a minefield…
I guess you could do the same thing with zombified cattle… And birds… And spores… And shrubberies…