I have not tried it too much with MTW2, but in RTW it worked extremely well against armies trying to cross bridges and if you didn't have enough men to block it off with spears.

Get about 8 regiments together, start them spinning and target the first regiment or two it look as though a machine gun just razes them all down. Moral drops like a rock, they break and you can repeat it on the others. It gets pretty interesting though if they have cavalry too. Looks like they are diving into a whirlpool and getting blasted from all sides.