I find everyone depends on me for one things: analgesics.

As I get headaches every day, I carry a multitude of pain killers. From Exedrin to Motrin to prescription stuff, I usually have a lot on me. I don't mind sharing.

I always feel better when I can help someone alleviate their own headache.

Other than that, the things people ask to borrow the most are a flashlight (to see behind/under desks) or pliers (to deal with recalcitrant network cables, etc.).

My loaner light is my Princeton Tec 20. As for the pliers, people smile when I hand them my Leatherman Wave. They love having an excuse to use/play with one.