ID includes your driver's license, any other government issued id, FCC operating license.
Radio can be an HT, mobile, or base, or any combination
Most deployments will be in noisy situations. Headphones are usual a must.
Food and water means enough water for your needs for the length of the operation. Hydration systems are great. You might want to keep an empty water bottle in your car and fill it from the litre or larger water bottles as needed. Keep non-salty snacks in your bag (gorp, fruit snacks, Power Bars etc).
Money: Both coin and paper. Do not expect your cards to work.
First Aid kits: We are not first responders, but you would be amazed how many times I have cut myself.
Sleeping bag is good to have if you get stuck at the site.
Flashlights: There are so many to choose from. Get one that has the most flexibility in terms of power. Lithium powered lights provide lots of light, but 123 batteries are not easy to come by in large quantities while AA and D are. You may or may not want to have a “headlight” as well. Again, batteries are a consideration.
Multi-tool: A Leatherman, Gerber, Swiss Army knife all work. You want something that cuts cable, strips wire and spreads peanut butter. Some areas will NOT let you take knives into them. Be prepared to drop your tools at security check points.