I have never owned a perfect knife.
But I have had a couple that I love dearly. The first I discovered at a flea market was a Phillipines Barong, with "Phillipines 1945" with some artwork chiseled into the side. It was mine for $40. Ebony handle carved into what I think was a dragon to the Philipino people, slight surface rust that I was able to clean to a beautiful patina. It was almost exactly the same length as a Ka-Bar, but just over half the weight, and the sexy curvature of the blade gave it more cutting surface than a Ka-Bar. The balance was impeccable. The sheath was unique. It'd been neglected and was brittle, but some loving application of oil returned it's lustre. The knife evoked such feelings of power and joy that are hard to explain, and understandably hard to understand unless you've held a tool made for your hand. Sadly, this knife was lost. I think in Pennsylvania on an ill-fated trip one Easter weekend. Also sadly, this is the closest to perfection that I think I've ever owned.
Along with my barong, I lost a Ka-Bar. They were together at the time. I didn't hold any special affection for that Ka-Bar - it didn't stand a chance along my barong. I did, however, purchase another Ka-Bar that I took to war. I had long since sharpened the edge to a perfect mirror's edge, and with the skillful application of some 550 cord, made the sheath more useful and convenient than it comes stock. This knife, with it's oiled leather handle and sheath, stamped "USMC", makes me feel my Marine Corps' heritage. It came back from Iraq with me, marked but still useful.
Sometime in the preparation for my deployment, I purchased a Kershaw Echo. A Ken Onion design of AUS8A steel, is a sight for the hands. While a far cry from the feel of my barong, it's organic curves simply makes it feel good in my hand. Point up or down, it feels an extension of my hand. It's heavy. The handle (a nylon / glass mixture, I believe) and full tang makes it very solid. The balance is in the hand; you don't throw this knife. (Like any knife, with the requisite knowledge and experience it could be thrown, and well, but this is the one to keep on you...) But I find that wearing a belt-knife gets you sidelong looks...
On the topic of Multi-Tools, I've owned several. Either after Boot Camp or MCT, I purchased a Gerber. The flip-out kind, with NeedleNose Pliers. I remember somebody specifically telling me to get the NeedleNose, and they couldn't have been more right. As a bonus, the tools all opened from the middle and locked via a sliding mechanism at the end of each handle. I had those for several years, and got a lot of great use from them. I'm not sure, but I'm pretty sure that I lost them. I really loved this tool
When I won Marine of the Quarter, along with a Meritorious Corporal promotion and a very nice plaque, I'd been awarded a Leatherman. I still had the Gerber, and the Leatherman probably would have seemed a nice tool on it's own, it couldn't compare to my Gerber. It was smaller and lighter than my Gerber with a pretty equivalent tool selection, but it just didn't feel as rugged. This proved itself true when I broke it in Iraq.
Which leads me to my final Multi-Tool to date. I wanted another Gerber, and at Matt Burton's recommendation, I got one with Spring-Loaded pliers, the Legend. He said that they'd change my life (or at least my view of such things). I was skeptical, but in the end it proved that he was right. (I'd thought that I was getting by just fine without the springs. Silly me...) These were more expensive than I'd planned originally, and took a LOOONG time to get to me. In fact, they took so long that I only needed to use them a couple of times before leaving Iraq! With that said, six years later, and I still have this pair, and still love them. They provide a comfort in knowing that when I put it on my belt, I can meet most common tool needs in comfort.
I've carried a variety of folding knives pretty much since the day I got out of Boot Camp, if not sooner. Most have them have been Gerbers. I've owned at least three Gerber EZ-Out knives. Since Nate McCallum showed me how to open it one-handed, I was in love. A strong curved top and tip, followed by wicked serrations, this was a lightweight knife that took care of the daily needs well. It, too, felt reasonably good in the hand point up or down. The weak point was the handle - it was a flexible plastic. It helped to keep the weight down, but it was pretty flexible. Though, keep in mind that this knife was balanced so that it could be easily thrown as well.
At some point, I got something a little less viscious-looking than the EZ-Out and went with another Gerber folder. I never knew what this one was called, but it was a more-conventional-looking knife. Black-painted half-serrated blade, slightly gold-colored rubberized handle. I had a couple of these that served well, but were ultimately forgettable.
While looking for my next everyday-carry knife, I saw an impressive-looking Buck folder at a counter. At my usual purchase price, but letting the Buck name reputation get the better of me, I bought it. It was heavy and sturdy, but it really was not a good knife. Sadly, I carried this thing around for a few years before realizing that I don't like it! The first thing that I noticed was that there was little-to-no care taken to the comfort and fit to the hand. Somehow I let this go... Second, it became apparent that whoever designed the clip had never worn the fucking thing in his pocket for a normal day - I kept snagging the stupid thing on everything. Worse, instead of just bending the clip, it tore gouges of everything it caught on! Eventually I realized that if I ever got into a situation where I had to depend on this knife for my life and safety, I'd have to worry about the clip gouging out my hand!
Faced with this realization, I went back to a knife that I really liked. I saw that Kershaw does have a foldout knife that looks spiritually related to the Echo that I dearly love, in the Blackout. Another Ken Onion design in 1550ST steel, with my favored half-serration, this knife is pretty lovely. The grip weighs less than I'd expected; the tang of the Echo is a higher proportion of the weight than I'd expected. This is not a deal-breaker. Especially when you find that the blade is spring-assisted! I can't express the simple joy that this little feature brings! And this knife comes with quite possibly the finest shipping edge that I've ever seen. I really like this knife, but there is a minor flaw - the handle. There's simply too much handle. I took my Dremel to the handle opposite the liner-lock to make it easier to disengage the liner lock (you should be able to easily close the blade), and to make the thumb-stud a little easier to get to. Also, after I'd put the dremel away for the night, I realized that the thumb-ridges on the back of the blade are likewise almost completely covered by the plastic (where it's prominent on both top and bottom on the Echo), and there are NO ridges on the bottom (where your thumb would be in a blade-down hold)! I have yet to make these grip modifications, but I will soon. With all of this said, I am very happy with my Blackout, and so far highly recommend it.
Finally, I would be remiss if I didn't mention Swiss Army Knives. Per my Father's recommendation, I think that every SA knife that I've owned was a Tinker. Two blades, two flat and a Phillips screwdriver, and an awl. All useful. I think I've owned at least three of these things, the first being a black Boy Scouts edition. I've always loved these for their versatility, but I've always been concerned at the flexilbity of the steel. But still, it's hard to go wrong with a Swiss Army Tinker.