Dig the Giro Phase Helmet
I have a big awkward head. This is one of the few helmets I found that is adjustable and makes my odd noggin' just about bulletproof when riding. I chose this helmet over a few others because of the great coverage in the back of the head. It does weigh a little more than similarly priced helmets in this category, but a few extra grams of helmet for more coverage is a small price to pay when you fly over the handle bars.