The Jackhammer is a two-handed mace good for warriors, paladins, and shamans. It offers a haste proc (63.2@45), relatively high DPS and a nice looking model. With a Paladin's Seal of the Crusader it offers a 1.37 attack speed, nearly half. With a Shaman's Flurry and zerking, it has 1.102 speed.
The estimated drop rate of this item is very low, around .01%. However, according to Thottbot information, the highest drop chance is from the Stonevault brawlers.