Uniquely useful thing you bring?

I'd love to get some feedback on some things people bring to EF that aren't common. Things that aren't found on guides/packing lists that you think are necessities. For me, it's icy hot. It saves my sore ass muscles after dancing all day and night. I highly recommend the stick form over the tub; the stick may get grimey but you can clean it off with a baby wipe. Would love to have some fresh input!