For the last 10 years or so I've carried a few of the teeny $20 Swiss army knives (finger nail knife?) and some of the bigger SA/Wegner pocket knifes but I've always found the bigger ones always felt bulky in the pocket.
Recently I've become enthralled with Spyderco knives. I've picked up a Delica 4 (full serrated) and an Endura 4 (combo edge). I have big chubby hands so the Endura sort of feels better in hand, but the Delica 4 certainly feels nice and unobtrusive in the pocket, even while at work in a business casual environment.
I am looking at sharpening systems now with Sypdercos Sharpmaker leading the options.