1. Exposure Protection – this could be wetsuit or drysuit with undergarments. Also included here are hoods, gloves and boots.
2. Fins
3. Buoyancy Compensation Device – the "jacket" worn to help control neutral buoyancy.
4. Tank
5. Weights
6. Regulator Assembly – the typical set up is first stage, primary second stage, alternate second stage, and pressure gauge
7. Timing Device or dive computer
8. Mask
9. Snorkel

That is what is worn. There is other gear that is taken along, but I wouldn’t call it "worn gear". These are things like a camera, cutting tool, signaling device, line, etc.