Minor cuts - super glue or I just use paper towels and electrical/duct tape.
stripped countersunk allen screws head - if you can't pein the hex back into shape use a hefty center punch and force a 'dig' off center then drive screw out with axial hits (hard to describe)
35mm film canisters - poke a small hole in the lid's center, wind up a bunch of solder. Poke the inside coil end of the solder thru the hole. Easily fits in the hand.
Also dump some solder paste in one - those metal cans leak and mess up your tool kit
I carry 15W Ungar Princess and a propane solder iron. I made up a PVC pipe with end caps to protect the propane unit - looks like a pipe bomb though, so I wouldn't recommend airplane travel
Nytril examination gloves keep your hands clean in most gunk out there. Keeps the schematics clean. Last longer than latex gloves
Double flute taps seem stronger to me and the points work nicely as a QND center punch.
DIGITAL CAMERA! - I now shoot before and after shots. Beats hasty hand sketchs and is a great CYA - wire colors and labels right there on your laptop.
Diamond hones - I carry diamond hones to touchup carbide and HSS stuff. Ever have a boogered keyway on a hardened steel shaft? Diamonds. I even carry a 1200 grit credit card sized hone in my wallet - knock the scratches off a hydraulic piston before replacing the seals AGAIN!
Learn how to sharpen drill bits, taps and step-drills
METRINCH kit - definitely! Boogered heads? 14mm or 9/16s? Who cares. I've stuck a 1/2" impact wrench on them and that bolt WILL COME OUT!
Mix ATF and Slick 50 at 50/50% for emergency bearing lube, makes great tapping fluid
Nice flexible comfy nylon looking knee pads - Us old pharts have trouble after a 4 hours on the concrete
Anyone use a bill cap with LEDs for lighting?
And the list goes on...
Rod (The CNC Dude)