I always had a phone with me. It was part of my job...

For sake of my sanity at work I always had my tablet and/or kindle, various chargers, cables.

swiss-tool, and pill fob on keychain.
Leatherman squirt Ps4
Lighter (Refillable Butane)
Quick release paracord bracelet w/ Whistle
Flashlight
Bandana
16GB usb key

Here's my two cents on bandanas. You can use it in a lot of ways, even when your not at your 100%, meaning no fuss or extra work required. Cutting up your shirt, pants can leave your skin exposed to sun, cuts, burns, etc.. If I have room, I keep on with me.