With 2041 posts under your belt, can I assume that you have been doing RC for a while?

Let's not assume, based on your header tank discussion....

Basic Building Tools:
Hex drivers
Phillips screw drivers
Flat tip screw drivers
Pitch gauge
Ball link pliers
Needle nose pliers
Hobby knife
CA glue / epoxy
Blade balancer or appropriate technique
ball link sizer
engine locking tool
threadlock

Field box tools:
voltmeter
charger
fuel pump
starter W/ Appropriate adapter
Glow driver

Advanced tools:
Rotor head tachometer
swashplate leveler
Calipers
tools for balancing blades depending on your technique

Those are the ones that come to mind right now. If I had my field box in front of me, or if I was at my shop I could add some more to the list.

Rafael