Definitely Dinotte... Their 140L tail light is hard to beat, day or night. On the front, I usually run one of the 200L headlights, or a Light & Motion Stella 200N in blinkie mode.

Clothing and road positioning is another way to help increase your conspicuity in daytime. Those hi-vis orange and chartreuse reflective vests are good, and over the past couple of weeks I've been road testing one of those reflective triangle "Slow-Moving Cyclist" warning triangles from Adventure Cycling Assn. So far, I've been pretty impressed with it.