First, let me state that I'm not a big fan of the "one knife for all things" school of thought.
But, if it's what you want. . .
I figure a 6-8" knife is best as a do-all. Not too huge, but not too small. As a consequence, it won't really excel at anything.
One I might use for that role (only if I was out in battle rattle, and just don't have the room to carry a drawer full of knives) would be the Ontario OKC3S bayonet.
The M9 Bayonet makes a decent field knife as well.
I see you carry an AK, so a bayonet for an M16 isn't really needed.
Knives that are very good values at a good price:
Unlike its earlier incarnations, the new ones are powder coated, have the proper grind, including the right amount of distal taper.
Ontario Ranger RD-7
I prefer the Ready Detachment series for their 5160 steel. Very good spring steel. Only complaint is that the handles are a bit fat.
Ontario Spec Plus Task Force
Versatile blade. I find the continuous curve to be easier to sharpen by hand. With a perfectly straight edge, I end up curving it over time anyway. The curve also makes it good for skinning and butchering medium to large game.
What can I say? Becker makes some great knives, and Ka-Bar has kept the line up very well.
If you are willing or wanting a slightly shorter blade, my top pick would be the
Ontario RAT-5 also being a good pick
All are very functional blades, and all are under $100.