Fenders and good lights. Not some million lumen garbage, a good ~80-100lux asymmetrical headlight so that you don't blind everyone and a wide taillight with 180 degree viewing so you are visible from the side and never run it on a flash or strobe at night.

I am also a huge fan of a front rack with a basket so I can keep my eyes on cargo, and not need specialized bags to carry odd shaped items.