Warrior is one the classes I play the most lately since latest expansion (Cataclysm). I have used this macro for questing, raiding, pvp, duels, pretty much is always in the bar for anything. With this macro you can do decent dps if just want lay back and spam the button.

Macro might be outdated, please check the forums for up to date macros.

This macro will start off with a rend every time you change a target, if decide to reapply rend for some reason, because maybe it got dodge or forgot to keep it up, just hold "Alt" modifier key once and push macro once and then release the "Alt" key, after that the next move as soon the macro can it will be rend. After that is just a rotation and popping cooldowns, you can also add Bladestorm or Sweeping Strikes if desire, but I usually save those for when have a lot of adds.
Just remember, most of my macros are not perfect efficient in fights, is mostly for when you do not want to think about what to push.

Single target:

Macro Explanation:

4.2 Warrior - Arms Lazy Macro

Multi target:

Macro Explanation:

4.2 Warrior - Arms Lazy Macro

UPDATED October 1, 2011: Removed Heroic Throw, for some reason it stopped working on the macros.