Anyway, you have this big strapping seal on top of papa san, trying to drive that big K-bar through that skinny but tough VNs chest. It took a LOT of doing, because apparantly a chest will "grip" a blade like crazy, when the victim is struggling for his life! Plus his hands are on it and your arms too, pushing it away.
It was a long struggle, and eventually it went in and the old guy expired. (RIP, no hard feelings.)
The moral of the story was that a K-bar is a great knife for many things, but it's too damn wide to be shoving through anybody's chest if you're in a hurry. The seal telling this story was of hte opinion that a narrower "dirk" like knife (Sykes Fairbairn or other) is better for sentry stalking. You may intend to go for the throat, but you may end up having to drive it in, and wide knives aren't so good for this purpose.
What made me think of this is that fat tipped spear point knife XSRDX posted a few up from here.
The Busse is more of a chopper. It's a big, heavy, thick blade - almost a short sword - and a single powerful thrust, or solid whack in the right spot, should have the desired effect.
As to daggers, Gerber got it just about perfect with the MKII.