Night visibility

I think bright headlights and taillights are the most important. At least 300-400 lumens on the headlight. And less light is needed on dark country roads, since your eyes adapt. In the city, you are competing with all the car headlights. The roads go bright and dark between streetlights, which also makes it harder to see and be seen.

And one of the brighter taillights. I like the Cygolite Hotshot 2W (my BF review). In bright mid-day sunlight, the blinking caught my eye when the rider was a few hundred yards ahead on a recent group ride. I have it aimed slightly downward and it makes a pool of red light on the road behind.

At REI: Jogalite Wide Leg Band. I have two.
Some of the local group riders have these reflective ankle bands. Reflective from all sides of the bike. They really show up at night, and the leg motion helps a lot. Very comfortable to wear too.

Of course, the car headlight has to reflect off these, so they don't fix the problem of cars pulling out from a side street. But they should "wake up" an overtaking driver or an approaching driver turning left across my path.