generic tools:
- screwdrivers (spend the money on a decent-quality one with swappable tips, or a range of sizes)
- measuring tape
- assortment of rackmount screws
- pliers/vise grips
- flashlight, preferably one with a thumb switch and belt clip

access equipment:
- laptop, power cord, appropriate console cables
- DVD images of various OSes I might need
- blank CDs/DVDs, thumb drive

wiring/cabling/tracing tools:
- cable
- electrician’s scissors or wire stripper
- pinout cheat sheet
- crimpers, connectors, cable tester
- fish tape
- mini butterfly hairclips for temporary cable marking
- velcro cable ties, zipties
- loopback plug
- punchdown tool, toner
- cable stretcher
- colored tape to mark patch panels for cable runs that need multiple hops
- label maker

just for me:
- sweater, iPod/earplugs, caffeine and/or sugar
- hardhat, depending on whose DC it is
- cellphone, ID & keycard (these stay on my person at all times)
- emergency phone numbers (should be posted in DC)
- paper, pens, clipboard
- sharpies

things I expect to be provided:
- ladder/stepstool
- access to restrooms
- lights
- cart