Special AI Mod 1.7.10, 1.7.2 added different AI patterns to mobs to do just that... Oh wait, there is: Special AI!

Special AI adds a variety of new AI patterns to mobs, including: monsters idly breaking your light sources and certain blocks, an attack AI for "passive" mobs, mounting AI, and a pile of unique combat AIs to keep you on your toes!

Each AI added by this mod can be disabled and configured, while most can even be enabled/disabled per mob, including for mobs from other mods! The properties file is generated in the 'config' folder in your .minecraft directory.