1. Lights. Making it easier for others to see you and for you to see the way.
2. Some kind of shield to protect your eyes/glasses from water; making it easier to see.
Could be the bill of a helmet or baseball cap.

3. Fenders. Keeps you and your bike clean(er).
4. Apparel based on temperature and your personal preference. Totally waterproof
jacket will block out rain; but may make you sweat too much.