There is no 'best' combat knife because there is not just one situation when you would use a knife to fight. If I am being put into a gladiator arena and I can only use a knife I pick a very different knife than if I was in the military and was being sent out on a 5 day patrol... and neither of those knives are what I would pick as my EDC in a modern urban environment. Knives are a constant trade off between effectiveness and practicality. The most effective knives for combat are going to be too big and heavy to carry long distances. In the age of firearms a really effective combat knife is less effective pound-for-pound than a much smaller knife and a handgun... and extending the concept, that knife+handgun is less effective than a rifle. This is why armies don't issue bayonets anymore. Pound for pound you are better off with another mag or two of ammo.

So to answer your question in today's age I say that the knife must have utility above just being a combat knife. It must be a combat knife and a utility knife... so I go with the Ka-Bar. It is a solid combat knife AND a solid survival knife.

Stiletto or Tri-edged knife. The shape of the blade means the wound won't close.