I have three helemts:

1) Specialized S3 - lightweight, very cool/vented, very comfortable. Doesn't leave my apt - only gets used on rides to and from home. My favorite.

2) Specialized sworks Evade - "aero" - for racing and fast group rides exclusively. Not the biggest fan of how it looks or feels, but supposedly it's fast so hey I'll take it.

3) Giro Savant in high-vis neon yellow. Use this for early or late rides when light is low, for mountain biking, casual rides and any ride that I drive to that isn't a race. Probably gets the most use although 1) is close.