My MagicShine 808 headlight is fantastic. Super bright and easy to mount/remove. It's got three brightness levels. Ultra bright, regular bright, and "help-the-cars-see-you" bright. I usually leave it off during the day and keep it on regular bright in the evening. If I'm going out in the dark, I use ultra-bright.

I just got a taillight, the Cat Eye Rapid 3. It's nice and bright for the dusk/dark but is pretty useless during the daytime (if you're looking for that). Three modes: steady, blink, and seizure. Steady only uses the center LED, blink only uses the two outer LEDs. Seizure uses all three and is definitely attention-grabbing.