There are several tools I have found extremely handy as a theater technician; chicken sticks, maglights (now, alas, superseded by LED flashlights), but many of those tools are really more like, well, substances.
10) Varathane Diamond Finish. Mist it over the paint job, give it a couple of coats, and even tap shoes won't scratch it when you are done. Available in matt through high gloss.
9) Diet Coke. Believe it or not, this is the secret ingredient you add to the mop water to keep dancers from skidding off your Marley.
8) WD-40. Often abused and sometimes maligned, it is the quick and dirty lubricant and cleaner for most things metal that you don't mind getting greasy and smelling of chemicals.
7) Sillie spray. The good brands of silicon spray lubricant leave an invisible film of liquid teflon to help drawers glide, pulleys work cleanly, and even stop floors from squeaking.
6) Foam mounting tape. Hard to clean up, but fast and secure for holding those little bits of audio electronics to a table or shelf where they won't get knocked down and trod on. Works really nice inside project boxes.
5) Board tape. Also known as artist's tape, this low-residue smooth-surface white tape is the ONLY tape that should be applied to the surfaces of mixers and other audio gear in order to mark channel assignments.
4) Nexcare flexible tape. The only hypoallergenic micropore tape for sticking wireless microphone elements to actor's fragile faces. You can buy it in rolls and save a bunch over the (handier) tape dispensers.
3) Goo Gone. Nothing removes the slimy residue of old tape from cables like this stuff. I buy mine at Wallgreen's.
2) Tuner Spray. Specifically, Caig de-oxit. Don't get the Radio Shack crap, pay the money for Caig. This stuff penetrates any switch or potentiometer to get out the crackles, and should be sprayed on every connector as part of your maintenance. Don't use it on faders though.
1) Gaff tape. Gaffer's Tape is NOT duck tape. It is stronger, it tears cleaner, it is available in matt black, it bears up under heat and moisture better, and it doesn't leave anywhere as much nasty sticky residue (nor turn into what duck tape turns into after a few weeks out in the open). Do not bring duck tape into a theater. Ever.