Damage Types: Pierce, Slash, and Crush

[licker]

I might add that if what you are really after are better differentiators between otherwise quite similar units (though I don't have a big problem with the similar units, I mean there are over 1000 units, you can't make them all *that* much different from each other) a more reasonable approach is to simply change some of the statistics for the weapons that they currently have. Changing the resource cost(down) would be a big incentive on most units, as would tweeking the length of some weapons (expanding the length scale a bit would help here).

These are simpler changes that could achieve the same end result, and be done much more easilly than adding an entirely new damage and resistance system.