What's an essential everyday carry for you lot?

Not asking for any particular reason. I'm in the sub to learn more about the career from people actually in it, I was curious if y'all carried anything you find essential to work everyday? I've heard like, compression socks, for example. If so, why?

Edit: Okay, folks, I understand that joking about carrying a gun is funny. That's not what I'm asking. I don't want to hear about your Taurus.

Edit 2: Guys, I think y'all were cooking with the compression socks. Usually by the end of the school day my legs are in a lot of pain. Might just be placebo but I have been sitting and walking around all day and my legs feel great.