I'm always carrying my Leatherman Squirt P4 micro multitool (pliers). Very well built, very small and light, has all I need to maintain computers at work, and for everyday needs.

Another knife which is very personally crafted, compact, and _truly_ always with me (yes, even in the bathtub!) is my 3/16" long blade thumb-nail. Properly shaped and properly sharpened every other day - it is perfect for opening mail and cardboard/plastic packages, cutting strings and tapes, opening latches in plastic laptop cases (and other electronics) without damaging its finish, and also works as a quick PDA stylus substitution.

My every day carry knives are a Benchmade Griptilian and a SAK Executive. I use these as most of us do to open boxes, cut string, tape, tubing, plastic seals, etc. I work in a laboratory environment. Of I'm outdoors I carry a neck knife, usually one of my own or an A.G. Russell Woodswalker as well as a sheath knife ranging from an old 1930's KA-BAR hollow aluminum handled hunting knife with my own mini kit in the handle. (This knife was made before the way "Rambo" knife craze spawned every cheap knife in the world with a hollow handle.) or possibly something more substantial or lighter depending on where I am and how long I will be out. If I'm camping I invariably have one of my Philippine Bolos as well. I use this for chopping fire wood and other heavy duty jobs. My maxi kit always contains one of these to be used not only for chopping wood but for building shelters, making traps and other improvised equipment out of wood, cutting vines, splitting small logs, butchering game etc.
I have been a knife colector for many years and I choose my carry knives much the same as most men choose their clothes for the day, taking into account necessity, portability, style, and just a feel for a certain knife on any given day.
Kix

I totally agree Falcon,
Look at any serious survival school and the one piece of equipment that they will tell you that you really need and can do the most with is a big substantial chopping knife. If you have this one piece of gear you can make it. All the other tools like multi tools, saws, axes, etc. are nice to have and can extend your repertoir of capapble tasks, but IMHO you simply gotta have the big chopping style knife. There is always one in my vehicle and my bug out kit for this very reason.
I also agree with your plan for unexpected events, go to Wal-mart and get what you need if nothing else is available. The problem is, once an emergency of any magnitude occurs, these are the first things that disappear from the store shelves, taken by all the num-knuts that neglected to prepare. Example: There was a lot of looting in Wal-Mart stars and others after hurricane Katrina. The news showed people taking color TV's and Stereos but the stuff that went first was food, water, tents, batteries and other camping/survival gear like propane cartridges, stoves, ponchos, bug repellent, etc. If it had been a colder environment things like sleeping bags and warm coats would have topped the list.
Kix

Today I used my knife to:

Open several boxes and to go through the plastic and paper wrapping.
Cut open a couple of blister packs.
Cut and pry off excess shims.
Cut through some rope.
Trim off a little wood to smooth out a saw cut

I EDC a LM c301 folder, LM Blast and LM Micra.

Fortunatly for me I convinced my company to puchase a couple of the folding and locking box cutters. I use it at least 10 times a day for various tasks from boxes, rope, bags, packages, etc, so my EDC blades do not take all the extra work abuse.

I also use my knife for peeling apples for my daughter. I imagaine others do that too. My LM has a blade launcher and lots of times people think it is a switchblade. Kind of funny because I get a good chuckle out of people who know nothing about being prepared. Was that cynical?

EDC is also Benchmade Griptilian.

Use it daily for cutting fruit & veggies - depending on what is in season. Yesterday 4 oranges & an apple. Summer time it cuts a lot of garden fresh tomatos - 3 months to go!

I have a large Kershaw fixed blade that is always in my truck. But working in a cubicle behind a desk doesn't require a large knife very often.

Also I have a Gerber Magnum LST Jr in my drawer at work, in my EDC backpack and several at home.

I like to cook & make a lot of stir-frys, salads, etc. so the Benchmade also cuts up a lot of veggies.

I personally carry a very small non-locking Buck pocket knife with a blade around two inches for most everyday tasks. Thats my "gentleman's knife" for peeling oranges, opening packages and cutting string. Its camoflauge for people that aren't comfortable with knives, and I'm not to concerned about losing it since it was a ten dollar knife.

I also wear a small mora around my neck for larger cutting jobs and 'just incase'. Its basically a fix blade pocket knife. It doesn't get used much because I can usually get by with the Buck knife.

Right now I'm experimenting with carrying a large mora, a five inch blade, in a horizonal sheath on my belt. I'm waiting for it to find its own niche or become enought of a hassle to stop carrying it. Its large enough for heavier work, but light enough to carry relatively easily. It'll be mostly for outdoors stuff, making kindling and food prep.

My EDC knife normal uses? Not very exotic: (1) opening bags of horse food when those string-pulls break before you get the bag opened, (2) slicing tomatoes in my lunch bag, (3) cutting various strings and cords. That's about it for routine uses.

When hiking, always accessible in case I have to quickly take down an angry grizzly bear or rabid buffalo, but that hasn't happened yet...

my EDC is an Elephant Toenail..short,with a heavy,wide blade
and a handle you can grip..the big blade is 2 inch by 3/4 inch
and the small one 1 1/4 by 1/2..it drops right into the watch
pocket of my jeans where i don't have to dig for it among the
keys and change..like everyone else it cuts twine..box's fruit.
the Toenail is a rope knife from the days when rope of some
sort was as common on a work site as power tools are today..
camping i carry a lock blade Sod Buster..the Leatherman and
a small Gransfors hand axe are carryed in a "daybag" for
everything else..

I live in an urban area so my everyday carry knife is a large SAK with a locking blade. I use it almost daily for opening letters, opening boxes and small repairs. The SAK seems a pretty good choice for that. I have a Leatherman Wave but don't carry it nearly as often. It has many more functions than a SAK and I love it but most of the time all I need is a knife blade and the one on the Wave just isn't that good.

Outdoors I tend to use a knife a lot more and for heavier tasks. These days it's my Kabar most of the time. It sees a lot of use, mainly carving wood, preparing shelter poles or a walking staff, making fire (with a magnesium firestarter), cutting twine etc. On shorter daytrips I can do most of the chores with a smaller Scandinavian fixed blade or even just my SAK, but on longer trips I really appreciate having a larger sheath knife.

One time when I was stuck in the middle of a steep icy slope I actually had to use my Kabar as an ice pick. I'm glad I carried it that day, I can't imagine getting out of that situation with anything smaller or less robust.