Go-Bag, Deployment Kit, Fear-Gear, etc. Whatever you call it. there are several items you should have with you during any deployment or activation. Preferably, they should be packed into a kit, a box, bag, briefcase, whatever, kept in your vehicle or ready to grab and go from home.
Here are some ideas for what to have in your kit:
Greene County (Ohio) ARES has a list of suggested items on their Jump Kits Page.
Orange County (CA) RACES has a very extensive suggested emergency supply list.
The ARRL provides a checklist as a downloadable PDF and in hardcopy format.
They include a checklist in their ARES Field Resource Manual
The most important item to bring with you to an event is:
A POSITIVE, FLEXIBLE, MENTAL ATTITUDE.