This is an elaborated ticket on MC-26678 (mods please close the other one)

In 1.2.5 SSP and before the little wobble to the whole viewport that occurs when you take damage used to indicate the direction the damage came from. As part of the 1.3 client/server merge, this behavior was lost.

Steps to view correct behavior:
1. Revert to 1.2.5 SSP and start a new creative world
2. Build the contraption as shown in the image attachment below
3. Fill the dispensers with arrows.
4. Exit MC and use NBTExplorer to change the world to survival mode (alternatively play survival until you obtain those items or open a copy of a current world)
5. Facing forward, strafe left into the left pressure plate. Arrow will hit you and the viewport will tilt to the right, simulating the head whiplash.
6. Facing forward, strafe right into the right pressure plate. Arrow will hit you and the viewport will tilt to the left, simulating the head whiplash.
7. (Cool part) Facing forward, walk into the front pressure plate. Arrow will hit you and the viewport will tilt DOWN, simulating being hit in the top of the head by something
8. Facing forward, back into the rear pressure plate, Arrow will hit you and the viewport will tilt UP, simulating being hit in the back of the head and having forward whiplash.
9. This seemingly "cool aesthetic" actually has real gameplay value because it indicates to fighters where incoming damage is originating from.
10. Repeat all steps in 1.8.1-pre3 (no need to use NBT editors just open to lan with cheat mode to switch gamemode). Notice how the viewport will always tilt right no matter what.