Bukkit

Version B:

• Fixed a bug where silverfish could sometimes spawn under players feet when using mega-aggro on PigZombies or Spiders.

Version A:

• Fixed a bug where bats were enabled in naturalistic bonus spawns by default.

Patch notes:

• Updated for Bukkit 1.4.6 ONLY.
• Fixed mega-aggro which was broken by the new build
• Added support for the new mobs
• Improved mega-aggro algorithms
• Wither Skeletons can use mega-aggro
• Mobs spawning with armor and weapons has not been added, since this functionality is already granted by adjusting hp/damage.

* No custom armor or weapon spawns, though hp/damage is covered by other functionality long before it was released on vanilla.