I always have at least two or three HideAwayKnives on me at all times. As a civilian government employee, I can't carry my Kimber at work, but my UHAK neck knife somehow ended up on the outside one day and NOBODY NOTICED. Not even in meetings. Of course, I normally wear three badges, three proximity cards, a pager (they're too cheap to issue us cell phones), an idisk, two conventional master keys and a gasboy key around my neck. Probably disappeared into the crowd.
The UHAK is for opening boxes and such. The Brock Midnight Claw on my belt under my shirt is for defense, and the Ankle Claw is for last-ditch defense.
I used to carry a Spyderco Matriarch with a Delica for box-opening duty, but in force-on-force training I found the HAK's (training drone) are the only blades I can use reliably when the fit hits the shan.