I used to have a friend who would forget to turn her lights on all the time, claiming that she could see fine so she didn't need them. Ok, but lights are on your car 50% so you can see shit, and 50% so other cars can see YOU. Especially in inclement weather, if it's foggy or raining heavy, yeah, it's daytime, but turn your freaking lights on, your car is fucking fog colored.
My favorite lights are those super-bright ones, the blue/purple LEDs that are brighter than most peoples' brights. My roommate is adamant that those lights should only be on cop cars and motorcycles, since it's especially important to see those types of vehicles at night. I'd add people who live in the country to that list, they'd be pretty useful out where there's no streetlights, but you never see them on a farm truck, they're always on some fucking Lexus sedan that's never been near a gravel road. There's no need for them in town, it's never dark enough for them to be necessary.