I also found peroxide and band aids would have been useful if I had brought them. And extra extensions for the socket set.
I was intrigued by the range of people and their equipment. Some had a small bag, some a backpack full, and some had custom wheelbarrows full of tools and parts extracted.
It occurred to me that if I were 15 years old, and wanted some practice, I could flail away all day long and learn how cars were put together without suffering any consequences. At the end of the day, no matter how much damage I had done, nobody would know until I was long gone.