My grandma bought me these pencils a few years ago that were day-glo pink, green, orange, and yellow, with my name on them. (I have a VERY unusual first name, and she had my first and last name on there)
At first I thought they were really dorky, and they just sat in a drawer for the first couple years, but after I SMed my first show and realize that the one thing actors ALWAYS asked for was a pencil, I pulled them out, sharpened them all, and then kept them in one of the huge altoid containers for my next show.
A few days after the first rehearsal on my that show I saw one of my actors at the library with a day-glo pink pencil...and realized it was mine! It was only then I realized the true value of these pencils -- now I know when people steal them!
They have since become a staple in my kit and people in my shows know them as my pencils (including the box that has a piece of gaff tape with "not altoids" written in big letters across it) always ask if they can use those pencils (they don't want the regular wood grain #2s that I supplemented the pencil box with). I have NO IDEA where my grandma got them from but they're now on my christmas list this year because I'm finally starting to run out, erasers have worn down, etc.
Other staples of my kit include a deck of cards, post its of all shapes and sizes and colors, various cables (cat5, USB cables, RCAs) an extension cord, rosin and lambswool (I work with dancers), those little oral-b brush ups, a lighter, rolls of spike tape in various colors, different types of pain meds (for people allergic to one kind or the other), tampons, cough drops, and a three-prong to two-prong adaptor -- just in case I go somewhere that only has two prong outlets and my computer is a three prong. =).
Also: saline solution and a contact case. I can't tell you how many times I've had actors whose contacts start bothering them in the middle of rehearsal and they are so thankful I have that so they can take their contacts out. Just make sure to rinse and disinfect after someone uses it!
Sometimes I just throw some random things in there (like an old knick knack) so when someone's looking through it for something they'll pull it out and we'll have a good laugh over it. =)
I always think of my kit as an ongoing process -- something I'm always working on. Always finding new items to add to it. These posts have all been great!