Cleave is the warrior's first multiple target attack. It is also used by many high-leveled bosses that mainly use physical attacks. It is a 20 Rage skill that deals weapon damage plus a small bonus to two targets, the current targeted mob/player and their neighbor.
If a second target is present, the bonus threat from Cleave is divided between them.
Tips and Tactics
The actual Rage cost of Cleave can be considered to be 20 Rage + the Rage that would otherwise have been generated by your next weapon swing. In terms of efficiency, Cleave converts its initial Rage cost into bonus damage and threat, and then doubles (triples if glyphed, see below) the damage of your next attack at the cost of the Rage it would otherwise generate.
Currently, Cleave is the only multi-targeted Warriorability that both scales with weapon damage and can be used while in [Defensive Stance], and the only multi-targeted ability of any class that does not trigger a Global Cooldown. This makes it ideal for high-end tanking situations involving multiple targets.
Cleave, like [Whirlwind], may be combined with [Sweeping Strikes] in order to generate additional hits. Cleave's secondary target is the nearest enemy other than the Warrior's main target. For this reason, if the Warrior and all targets are stationary, Cleave will continue to strike the same secondary target. Shifting positions slightly will often change the secondary target, however tanks and dps alike should be aware that this may cause Cleave to break nearby CC if not used carefully.
[Improved Cleave] increases the bonus damage of Cleave by 40% per rank, up to 120% additional damage. Since only the fixed bonus damage is effected by this talent and not the total damage of the Cleave, it can be viewed as a non-scaling talent.
[Impale], 
[Improved Cleave], 
[Focused Rage]
20
[Defensive Stance], and the only multi-targeted ability of any class that does not trigger a Global Cooldown. This makes it ideal for high-end tanking situations involving multiple targets.
