What's actually in your kit bag for a latex event?

I am finally putting together a proper kit bag so I stop forgetting things at events. So far I have a shine spray and a cloth, a bit of dressing powder in a small tub, and flat shoes for the journey home. What else earns its place in there? I am thinking a spare in case of a wardrobe fail, maybe some wipes, and water. I would honestly rather learn from your well-packed bags than from a disaster on the night itself. What is the one thing you never, ever leave the house without now?