There are two kinds of people in this world: those who like skull caps and those who wish they did. For the latter who are always looking to get their ninja on, check out the Adrenaline Combo Skully beanie hat from Chaos.
The Skully weighs basically nothing, and is made from a thin 83% polyester, 11% wool and 6% spandex blend for just the right amount of four-way stretch. The Dri-Release fabric is machine washable, and FreshGuard anti odor treatment beats down the skull skank.
Chaos is highly focused on headwear, and the Skully is a very livable piece. With more people than ever seeing the light and putting on a helmet there should be a place in your wardrobe for a liner beanie. Once you've tried it you'll find it works just fine on its own too. And score: REI Outlet has it as a Special Buy!