Execute

Execute is an instant-cast ability learned by Warriors at level 16. Execute can only be used when the target is below 20% health. The skill costs 10 rage, but will convert up to 20 extra rage (if available) into additional damage. Execute has no cooldown (except for the global cooldown).

Talent improvement

 * Lambs to the Slaughter provides a stacking buff that increases damage by up to 30%
 * Sudden Death allows you to keep 10 rage after using Execute, making it constantly spammable
 * Executioner (warrior talent) causes Execute to grant a stacking buff that increases melee attack speed by up to 25% for a short time

Tips and tactics
When an enemy with a lot of health such as a heroic or raid boss gets below 20% health, both Fury and Arms warriors should change their rotation to spamming Execute. However it is worth refreshing Colossus Smash on the target whenever possible, and Arms warriors should remember to use Mortal Strike once every 15 seconds in order to ensure that the Lambs to the Slaughter effect remains in place, increasing Execute's damage by 30%.

The Sudden Death talent allows an Arms warrior to constantly cast Execute over and over, because it causes 10 rage to always be left over after using Execute. This makes Execute basically free.

During a long Execute phase, it is very prudent for an Arms warrior to use Deadly Calm, which will dramatically increase the damage done by making all of the Execute attacks be 30 rage executes instead of 10. Likewise, for either spec, judicious use of Battle Shout, Commanding Shout and to a lesser extent a glyphed Berserker Rage and rage potions can increase output during an Execute phase. The more rage available for your Execute to turn into pure damage, the better.