I don't quite understand why people gear up to commute. Of course there are always exceptions to this depends where you live and how bike friendly your area is.
Helmets, I guess never hurts and probably good practice to wear most of the time.
Eye pro, a must have in Portland area, especially Spring and Summer.
Lights, if you're riding at night, most places it's the unlawful to ride with out them.
Bicycle shorts, only if I was commuting >20 miles.
High vis vest/clothing, only when traveling in areas that are questionable and not as cyclist aware.
gloves, only if it's cold enough.