Helmets all look stupid anyway, so I got one that's light, comfy, and well-vented. If it's cold, I wear a cold weather cap underneath. I've got other caps for when it's rainy, too.

I also have a Bell Citi, bought when they were still available, including the rain cover and mirror. I haven't used it in ages, but it's hard for me to want to get rid of it since it's so uniquely versatile. Plus, I've always told myself to "never buy a used helmet", so I don't want to make someone else go against my own advice.