Depends on what I shoot, the "mission load" varies.
Normal shoot: 1 body, 2 or 3 lenses (WA/standard/tele), 1 flash, + 1 spare set of batts.
Paid shoot: 2 bodies + 2 flashguns + 2 spare sets of batts per piece of equipment.
Bad weather: + Raincoat for camera.
Other essentials: Basic cleaning kit (lenspen+blower). Facial wipes/wet tissues/regular tissues. Drinking water. Small clipboard + writing instruments. Small torch.