Here's my list:
- helmet
- air compressor
- pressure gauge
- torque wrench
Keep it simple, no need to bring everything. Some basic tools if you want. I usually also include non race car related items such as:
- long sleeve shirt (if required by track rules)
- sunblock
- water
- rag/cloth (to clean numbers off window at end of day)
- Aspirin/Advil/Robax
- kleenex
- bandaids