Blinkstrike

Source
This item is a random world drop.

Little Blinkstrike facts:
 * 1) Can proc off of itself.  (unlike some other extra attack procs)
 * 2) Can proc off of windfury and vice versa.
 * 3) Can only proc off of the second attack of reckoning (can proc off the first one but cancels out)
 * 4) Extra attacks can proc any other enchants.