Persuader

The Persuader was first crafted by a blacksmith who was having trouble collecting payments for weapons and armor that were purchased from him. After he let the Persuader "talk" to the clients, they paid up quickly.

Source
The Persuader is crafted by Blacksmiths with a skill level of 300 who also have the Hammersmith specialty.

The components are:
 * 15 Arcanite Bars
 * 10 Dark Iron Bars
 * 20 Essence of Undeath
 * 20 Dark Runes
 * 10 Devilsaur Leathers
 * 2 Skins of Shadow

The plans drop off the toughest creatures in Azeroth.