Windshear

During the Dark Brotherhood quest [http://elderscrolls.wikia.com/wiki/Hail_Sithis! Hail Sithis!], after you assassinate Emperor Titus Mede II, make sure you don't miss this neat little sword carefully tucked away on the main deck. Instead of following the quest marker to the back of the ship, where you promptly dive off into the water, head out onto the main deck of the boat.

After clearing the deck of all the Penitus Oculatus and sailor enemies, follow the stairs that lead to the prow (the front), which is majestically thrusting towards the sky. At the very edge is a gilded hilt, letting you claim Windshear -- a one handed curved sword (a la Alik'r ). What makes it so special is not just the name, but the enchantment: Bash attacks made with this weapon have a chance of knocking enemies down.