Wikia

Killing Machine
Killing Machine (Passive) Passive Your autoattacks have a chance to grant a 100% critical strike bonus to your next Obliterate or Frost Strike.
Usable by
Class	Death knight
Properties
School	Physical
Talents
Specialization	Frost
Level required	63
Related buff
Killing Machine 100% bonus to the critical strike chance of your next Obliterate or Frost Strike. Duration: 10 seconds

Killing Machine is a passive death knight ability learned at level 63 for death knights with the frost specialization.

Patch changes

Patch 4.2.0 (28-Jun-2011): Can now properly be triggered from off-hand attacks as well as main-hand attacks.
/ Patch 4.0.1 (12-Oct-2010): Now affects Obliterate instead of Howling Blast.
Hotfix (2009-04-01): "The weapon enchants Rune of Razorice and Rune of Lichbane will no longer cause the Killing Machine talent to be triggered more often. ^[1]"
Patch 3.0.8 (2009-01-20): Instead of a chance to be triggered on critical strike, this talent now has a chance to be triggered on each swing based on the swing time of the weapon (slow weapons more likely, fast weapons less likely).