Buck 3 inch lock back during the week at school (private school). The girls who work for me (it is an all girls school) doing network support are expected to carry a lock back pocket knife. More than one has told me after graduating that they now always carry a pocket knife.
Weekends include a leatherman and a pocket knife, size depends on where I will be that weekend.
When my son in law lived in Chicago, they would come down to visit on the weekends. I would meet them at the airport, give him (and my daughter) a pocket knife to use for the weekend. They would give them back before flying home. We often remarked that you kindof feel naked when you don't have a pocket knife.