Gloves of Haste

Increases the attack speed of the Hero by 15% when worn.

Gloves of haste are elbow-length studded leather gloves that can be buckled securely into place.

Source

 * Arthas can find one in Digging up the Dead, chapter 2 of the Warcraft III undead campaign, Path of the Damned.
 * Tyrande can find one in Daughters of the Moon, chapter 2 of the night elf campaign, Eternity's End.
 * Illidan can find one in A Destiny of Flame and Sorrow, chapter 6 of that campaign.
 * Kael and Lady Vashj can find one in The Crossing, the secret level of the Frozen Throne alliance campaign, Curse of the Blood Elves.
 * Thrall can find one in the Countdown to Extinction, chapter 5 of the demo campaign and the chapter 3 of the custom campaign (Exodus of the Horde).