Agree with the others on replacing the horn -- just haven't gotten around to it yet.
So people ahead of me can see me:
- SpyderPops LED Bumpskid
- SpyderPops Spyclops II LED
So people behind me can see me:
- Brake Free Helmet Light
So people anywhere can see me:
- SpyderPops Full View Turn Signals
- Hi-Vis Jersey/Jacket (depending upon weather and temp)
And of course, so I can Google their license plate after they DON'T see me:
- Lamonster RAM mount/Techmount TechGripper
What Peter said is really the most important part: always assume the worst of the other drivers -- they'll rarely disappoint you...