Zero Tolerance made a bayonet sort of along the lines of the M9, but it was a full tang design that ended up feeling twice as heavy as the original due to the thickness of the blade. I have one that I got off of Bladeforums, and it is sharp as a motherfucker - like, scary sharp - and it will lay your shit open with the quickness if you aren't careful with it. It makes a much better field knife than the M9 because there's no way you're gonna break this thing, and it has heft enough to make chopping an easy proposition.
My only problem with it is the excess weight in the ass end, which makes it feel bulky and lifeless in hand. I'm seriously thinking about perforating the tang underneath the scales and maybe doing some jimping to the spine of the tang and part of the blade just to shave a few ounces off this thing. It's a beast of a knife, but with a little work, I think it has great potential.