These are the items I consider essential:
(1) A small Swiss Army knife for every individual. These are inexpensive and have three kinds of screwdrivers, a can opener, a fish scaler, a small blade, a scissors, and most importantly of all, a tiny tweezers to remove splinters. The tweezers will really come in handy.
(2) A small knife sharpening stone. An absolute positive must. I cannot overemphasize the need for this item. A small can of oil for the stone.
(3) A small fine file. The kind you buy at Home Depot. This can be used to sharpen axes, chainsaw blades, saw teeth, shovels and edge implements. This will be worth it's weight in gold. Buy two. You'll lose one.
(4) A folding pocket knife, such as a Buck knife. Good for cleaning fish, gutting an animal, cutting steak, and whittling. Some have a little belt clip.
(5) Paramedic Bandage Scissors. These can cut wire, cloth and most anything. Purchase two. Plus a scissor holster. Get them at an EMT supply store or on the net.
(6) An inexpensive small box-cutter with extra blades. The kind with the break-off blades is fine. Purchase as least two. Very handy for cutting plastic bags or tarps.
(7) A K-bar Marine survival knife with a rigid sheath. I happen to have one of these left over from my military days, so I am biased. I like the leather handle. You require the hard synthetic sheath. NEVER, ever, carry a knife in a leather sheath. If you fall, the knife will go right through the sheath. Get the K-bar with the serated edge. These are very handy for firewood, opening cans, and cutting thick ropes and hawsers, providing you keep it sharp. I prefer the model with the steel blade, rather than stainless steel. It's easier to sharpen. You may have a problem getting into a FEMA shelter with this. They have confiscated them in the past. Hide it. Do NOT use this as a pry bar, because it will snap.
That's about it. Ninety-nine percent of your disaster/survival needs can be satisfied by the above choices. I know there are knife enthusiasts who will extoll the virtues of a Bowie knife and the Arkansas pig sticker. I leave them to their wilderness fantasies of becoming Davy Crockett or Daniel Boone. I like the wonderful varieties of knives available, have a couple in my closet, including a fighting Fairburn, but do not consider them necessary for survival purposes.
Using a sharpening stone is not difficult, but it is not necessarily intuitive. Do a "google" sratch and you will find several fine sites with explanations and illustrations. This is a "necessary" survival skill.
You will find you can purchase inexpensive sharpening stones in various grades from coarse to very fine. The small stones that are acceptable for survival use have two sides. One fine and one coarse.
If you have a sheath knife, such as a K-bar, keep your stone in a little "stone holster" taped to the sheath.
Never think "knife". Think "knife and sharpening stone".
There are arguments pro and con lubrication, but I believe lubrication with oil or water is a necessity. In an emergency there are ordinary stones found outdoors that can do the job. Many prefer to get rid of the final burr with a leather strop, much like the old-time barbers. The inside of a wide leather belt works just as well.
The blued United States military M-9 Bayonet is expensive but popular amongst survivalists.
They were invented by a company called Qual-A-Tech, under U.S. military contract, but are now manufactured by Phrobis, Buck, Lan City and Ontario knife manufacturing entities. Available at most U.S. army surplus outlets.
Depending upon the year of manufacture, these may be attached to your M-16 semi-automatic weapons in some states. Sylvestor Stallone is said to have liked them.
I don't have much to say about it, except they usually come with a hard scabbard and sharpening stone and have a built-in wire cutter when used together with the sheath.
There is a slot on the blade that attached to the bottom of the scabbard, where there is a wire cutting device. The sheath comes with attachments for the standard military web belt.
An acceptable survival knife.
There are two other bayonets to consider.
The M-6 Bayonet, with metal sheath, was designed for fitting on the M-14 7.62 NATO rifle. If you have purchased a Springfield M1A, as I recommended in another post, depending on the year of manufacturer, this may fit the rifle. For a period of time the "stud" upon which the knife was affixed was banned. It is no longer the case.
The M-5 series of bayonets, with metal sheath, are designed for the WW2 Garand, a gas-operated semi automatic shoulder weapon utilizing an eight-round clip.
For decades Garands were routinely issued via the United States male to any adult male demonstrating qualification as part of the Director of Civilian Marksmanship under the Department of the Army until 1996. Under this little known program the stock of military , 45 M1911 Colt pistols, .30 carbines and M-1 garands were distributed to the civilian population at cost. Every U.S. citizen was entitled to be issued one government army issue weapon in his lifetime, a choice of a pistol, a carbine with a 30 round magazine or a rifle. You could only choose one type. I got my first Garand in the mail from the government at age 18 under this program. My neighbors all received carbines.
The U.S. government provided free ammunition to all with weapons under this program for decades.
The older bayonets are too long to be useful as survival weapons.
Both of these are acceptable high-quality survival knifes and are often sold at a great discount as military surplus. Legally, there is an issue because bayonets are defined in the penal laws of many states as "weapons". You can purchase a "survival knife" in some jurisdictions, which is more lethal, but a "bayonet" is considered to be designed for killing. This is a good reason to shy away from them.
The positive side is that they are often available at gunshows for one fourth or less of the price of a new commercial "survival knife" with a similar blade.