Just one thought here- I'd like to be sure of what the OP is asking.
People often refer to fighting knives as combat knives. Very different things. Something like the USMC Kabar was designed and used in all sorts of utility roles. In fact, without any numbers at all to support it, I'd be willing to bet that it saw utility use an order of magnitude more than it saw use as a fighter.
Just want to clarify that the OP is looking for a rugged utility knife that could be pressed into service as a fighter even if that's not the primary purpose of the knife. Is that right?
If so, how about something like a Becker BK7? Similar in size to the USMC kabar, but tougher due to full width tang, and with the handle scales, you have options to customize. Comes in well under budget, great all round utility knife, and could do some serious damage in a fight if you know how to use it.