Bukkit

Description:
This plugin is as simple as the name implies. You type in /mobcap(or /mc or /cap) and you'll be able to right click a mob and make it your hat. If you don't own the mob like ocelots, wolves, or horses you can't equip it because you could just steal someone's pet. The only mobs that can't be equipped are creepers, the ender dragon, and the wither. I've made it that way for griefing purposes. Witches and ghasts will still try to shoot you so be careful. I didn't disable ghasts because it's hard enough trying to reach the thing in the first place. Sooner or later I will add a feature where you can have multiple mobs as a hat, but that is for the future.
Planned Additions:

• Make hostile mobs not hit you. /done
  
• Wear multiple hats /done
  
• The mob hat you're wearing gives you some sort of ability.

Permissions:

• mobcap.passive.cow
  
• mobcap.passive.chicken
  
• mobcap.passive.bat
  
• mobcap.passive.ocelot
  
• mobcap.passive.villager
  
• mobcap.passive.snowgolem
  
• mobcap.passive.wolf
  
• mobcap.passive.mooshroom
  
• mobcap.passive.horse
  
• mobcap.passive.sheep
  
• mobcap.passive.pig
  
• mobcap.passive.squid
  
• mobcap.passive.irongolem
  

• mobcap.hostile.zombie
  
• mobcap.hostile.skeleton
  
• mobcap.hostile.spider
  
• mobcap.hostile.witherskeleton
  
• mobcap.hostile.blaze
  
• mobcap.hostile.cavespider
  
• mobcap.hostile.ghast
  
• mobcap.hostile.silverfish
  
• mobcap.hostile.slime
  
• mobcap.hostile.magma
  
• mobcap.hostile.witch
  
• mobcap.hostile.pigman
  
• mobcap.hostile.enderman
  

You can use mobcap.hostile.* for all the hostile mobs and then mobcap.passive.* for all passive mobs. For complete access to the plugin use mobcap.all. There are no permissions to use the command as it isn't necessary if the person doesn't have any permissions for any mobs.