Okay, here goes:
On my duty belt I carry the department issued Asp, OC, department pager, and 2 way radio. I also carry a Twin-Task 3C flashlight - it can either use 3 LEDs, 6 LEDs, or a Xenon bulb and runs on three (department issue) C batteries. I also keep my cell phone, glove pouch with 2 sets of gloves, and a utility pouch with Gerber multi-pliers, window punch, and tweezers (handy for shell casings, crack rocks, etc.). I keep a GOOD folding clip knife in my pants pocket for quick access (handy for cutting fingerprint tape).

In my car bag I have a plastic box with about 30 hanging file folders for forms, a city map, AZ state laws, Tucson city code, a personal organizer (calendar), traffic vest, Mag light, tool bag with socket set, vise grip pliers, heavy duty stapler (for posting citations), and spare eyeglasses.

In the trunk I keep my camera, print kit, coat, evidence kit, syringe holders for collecting discarded hype kits, flares, traffic cones, fire extinguisher, first aid kit, blanket, dust masks and "bunny suit" for HAZMAT response, and misc references. If you have an *assigned* car, I'd also recommend carrying a broom for clearing debris from the roadway at minor collisions where no tow truck will be responding. In your climate, I'd also think about a small folding shovel and a bucket full of ashes or sand, a tow rope or snatch strap, and maybe some emergency Mylar blankets and candles. Here in Tucson we have the opposite problem, so we carry cases of drinking water for the dehydrated transients in our July heat.

Make sure you carry some hand sanitizer, latex gloves, and some kind of bleach water or antiseptic solution too. When you have a "stinker" or a dirty house you will appreciate it much...