I thought I'd thought of everything for every shoot (including Diet Coke and a Swiss army knife), ... but I overlooked a first-aid kit. Luckily, it was I, not a friend, who proved the usefulness of such an item, by slicing my thumb on broken glass in the grungy alley where Bink and I were shooting the Fly yesterday.
(Yes, I have had a tetanus shot within the past ten years.)