I have about a dozen knives(Couple benchmades, couple Spydercos, some Kershaws and a few others) I rotate out on a regular basis and NEVER leave home without one.
I have never been a big fan of the "swiss army" style knives(Victorianox, Wegner, etc) as they just do not hold up to abuse. I'm VERY hard on my knives and have broken half a dozen of those styles over the last 15-20 years. The leatherman style multi-tools are much better suited if you need a pocketable tool box.
My current two favorites are my Benchmade Griptilian and Kershaw Leek. The Griptilian is a stout knife and has a very usable 3.5 inch straight edge blade that accepts and keeps an edge like a razor. I've had this knife for about 4 years know and try as I might, I have not been able to kill it yet. One of the best and most durable knives available under 100 bucks, IMO.
Second favorite would be my Kershaw Leek(designed by Ken Onion). Fantastic knife and with the open assist, it is VERY quick and easy to operate. Again, this blade holds an edge that you can shave with. Only complaint about it is that the tip of the blade is a bit weak. I have snapped the tip off twice with regular use but Kershaw has always given me a brand new one, no questions asked both times.