I probably carry the Piranha Bodyguard the most during the week. Very slim and lightweight and easy to carry in dress clothes or athletic gear. Same can be said for the Kershaw Leek.
When physically working our in the outdoors, the Emerson Sheepdog is what I carry—you can see it is well used.
My son LOVES the Spyderco Harpy (that is mine in the picture, his is well used). He says it is the perfect knife for cutting net wrap from round bales, opening feed bags, cutting rope and twine (what it is designed for), opening boxes, gutting deer (the curved tip acts just like a gut hook) and gutting/cleaning small game. That is all he has carried since I gave it to him two yeas ago.
They are thin and lightweight so they are easy to carry, but VERY strong steel. They feel and lock-up like a bank vault in the hand.