In the US it seems that you get in a lot less legal trouble if you use a handgun for SD than a knife. In Canada you simpply cannot legally carry a handgun unless you are a cop or on the way to or from the range with a liscence that specifically allows handguns. I have a liscence where I am not even allowed to buy any more guns I can only keep the ones I do have and by ammo. We do have a lot looser laws about knives but self defence is pretty much illegal. If a cop asks you why you have a knife and you say SD you will be arrested and most likely get a lifetime firearms ban as well.
It is not all bad though. You can carry any size knife you want concealed or not so long as you don't intend to use it as a weapon. If you happen to be attacked it is legal to use it to defend yourself. Now just because it is illegal to carry a handgun it is just as easy to get an illegal one as in the US so you are quite likely to face a handgun when you just have a knife.
This also is not as bad as it seems. This will come as a shock to some of you but at the kind of ranges most crime related gunfights happen(within 20 feet) a knife is just as useful and deadly as a handgun often more so. Also the guy with the gun is probably not an expert marksman he may even be holding it sideways.
Most amateurs expect the gun to do all the work. There are some very good tactics for bringing a knife to a gunfight and winning.
There was a famous study done in the US where they took 40 experienced cops and had them face an attacker they knew in advance was going to attack them with a knife. 39 of them failed the only cop who passed happened to be a black belt.
The reason was they all went for their gun. A healthy man can cover 14 feet in 1 second from a standing start. Even backpedalling and knowing what would happen
they all failed. The black belt however got off the attackers line and then had plenty of time to get his gun out.
The point was that if you focus only on your gun you are dead. It is just a tool it is up to you to win the fight.
I have a lot of knives but my current favourite SD knife is nearly perfect. It is the Spyderco Mule team knife with a simple paracord wrap. It is very light and flat so it can be very easily concealed. It is the sharpest knife I own and is less than half as thick as the thinnest Scrapper. It's wide leaf blade would make huge hacking cuts.
Here is a photo of my Mule team knife that I have in pristine condition as a collectible. I can't wait for the Mule2 which will be made of CPM M4 steel but these ones are 52100.
http://picasaweb.google.com/Lance.G.Davis/SmallFixedBlades/photo#5185451129763944770Here is a photo of a few nice small fixed blades including my Wrapped Mule under the satin SS4.
http://picasaweb.google.com/Lance.G.Davis/SmallFixedBlades/photo#5185449166963890338One reason I prefer a knife to a handgun is it takes more inner strength and will to actually cut a man's throat than it does just to shoot him. I think that if people carried knives rather than guns there would be less people killed over petty squabbles. However that is also the knife's biggest weakness for SD.
It is quite hard to get over what you actually have to do even if your life is in danger.