You attempt to finish the wounded target off, firing a long range attack dealing 420% weapon damage. Kill Shot can only be used on enemies that have 20% or less health.
If Kill Shot fails to kill the target, the cooldown is instantly reset, but cannot be reset more often than once every 6 sec.
Kill Shot is a hunter ability learned at level 35. It is intended to finish off wounded targets. It is only usable when the target is below 20% health, but the unusually long range is paired with an enormous amount of damage. In PvE it has the potential to be one of the hardest hitting and highest critting abilities in the game.
Kill Shot deals 450% ranged weapon damage. This makes it scale very well with the hunter's attack power, making the shot deal exceptionally high damage in a raid setting, where the hunter is likely to benefit from multiple buffs that increase attack power, such as Battle Shout and Blessing of Kings.
Since it has an unusually long range, Kill Shot is useful for finishing off anyone who gets out of range of your other abilities in both PvE and PvP.
Against target with very high amounts of health, you should use Kill Shot as soon as you can, as the target may have enough health left for you to be able to use Kill Shot multiple times. This is especially true on bosses.
Patch 3.2.2 (2009-09-22): Minimum range of 5 yards added.
Patch 3.0.8 (2009-01-20): Cooldown reduced to 15 seconds, down from 35 sec.