If You hit a mob in creative mode, it wont come after you, as if you never hit it.
(Tested With a Creeper,Zombie,Skeleton,Spider,Slime,Cave Spider,Zombie Pigman and Witch.) (NOTE: The Zombie Pigman, Spider, and Cave Spider Worked Normally)
Environment
Windows 7, Latest Version of java, Minecraft 1.6.1 (Launcher Version 1.0.8)
Duplicate of MC-15111, please use the search function to see if your bug has already been submitted. Currently over 58% of tickets are being closed as duplicate.