joining a little late but...
I'm located in CA - unfortunately in Orange County where CCW's are rare since Sandra Hutchens took the Sheriff's seat. OK - rant off... things are what they are and when I got the chance to train with Mike Janich several years ago, I was amazed how much stopping power a knife has when it is used correctly.
To come full circle on the OP... good knife basics: a solid knife, with pointy 3"-4" blade, straight/non-serrated edge, slip-proof grip and solid locking mechanism will suffice. Pair that with anatomical targeting (meaning you aim for critical muscles and tendons) and bringing the knife to the gunfight can level the playing field - unless the person with the gun is good with movement and combatives.
This does by no means indicate that I would always prefer a knife over a firearm - If I could carry a sidearm, I would do so. However, having trained with Mike Janich directly twice (last time was this Summer) has increased my level of confidence in my knife techniques. I would highly recommend this type of training for everyone who carries a knife, whether it is as backup or primary. During the seminar in July we had people from 16 to late 50's adapt the techniques equally well.
The best thing about the system is that it is simple and intuitive and that many applications carry easily over into the realm of unarmed combatives.
So, as far as bringing the knife to the gunfight - it's not quite as easy as the ambush that Sean Connery set in the Untouchables. Try your gun material in a force-on-force setting against someone who has experience with the knife - make sure you are aware of what the knife is capable of, before you get monkey-trapped with your pistol. This is not bashing the use of a firearm - just an experience that I took from several force-on-force courses.