I've been thinking about this for a couple of days. I have no 1st hand experience in such things, but would tend to believe less is more. Of the knives I actually own I think I'd carry this.
Bradford Knives Guardian4 Knife 3D Green Micarta (False Edge/N690/Satin) - Blade HQ
This isn't one of the better known brands, but I picked one of these up a few years ago and I'm really impressed with the quality, functionality. If it comes down to a knife fight then I'm SOL. I'd just have to do the best I can, but there are a lot of utility things that can be done with a 4" blade.
I'd also consider my Becker BK16.
Bradford Knives Guardian4 Knife 3D Green Micarta (False Edge/N690/Satin) - Blade HQ
This isn't one of the better known brands, but I picked one of these up a few years ago and I'm really impressed with the quality, functionality. If it comes down to a knife fight then I'm SOL. I'd just have to do the best I can, but there are a lot of utility things that can be done with a 4" blade.
I'd also consider my Becker BK16.