It is possible to be a Camera Assistant with very few tools. You can almost do this job with these three items: (1) Swiss Army Knife, (2) Cloth Tape Measure, and (3) Flashlight.
The job is easier and more fun, however, with a few additions to this meager list. Every Camera Assistant is going to have his or her own set of tools that they carry. It will also vary from job to job.
I have broken my list into two sections, Essential and Optional. Have fun customizing your own tool kit.
Keep in mind the one basic rule about tools:
ALWAYS USE THE RIGHT TOOL FOR THE JOB.
There is also yet another codicil of Murphy's Law that applies to the Camera Assistants’ tools:
NO MATTER HOW MANY TOOLS YOU OWN OR ...