There are innumerable laptop sleeves in the world, but I can't say I've ever seen one quite like the Evernote Diver Sleeve. Rather than having a zipper or other enclosing mechanism, the neoprene Diver Sleeve simply stretches around the laptop like a sock, with pull-tabs at either side of the opening for super quick unmasking.

The Diver Sleeve comes in two sizes (13" and 15") and is $42 on the Evernote Market.