KP95OKC, do a search on "Japanese swords" in this forum and you'll hit about 3 threads that originate from about 2 months ago (which also happened to be the reason for my first posts here) ... anyways tanto ("tan" = short, "to" = blade) are shaped as such to punch through armor. Not really cut through a half-inch of steel plate par se, but the squarish tip can connect without snapping, and the pressure applied at the point is greater than your usual dagger (think surface area) because more of the weight of the blade is behind the tip, symetry-wise. And it slides along grooves in armor easier than, say a stiletto would. Tanto by the way are de rigeur weapons for yakuza, who prefer unvarnished wood handles and scabbards of one piece. If you're looking for tanto folders, Cold Steel would probably be it (though I don't like their marketing one bit.)
I haven't ever used knives in combat to be bluntly honest, but I think this is the sum of it. Wait for more experienced people to reply on this thread.