What does the zig-zag pattern on Hawker Hunter's leading edge represent?
After doing a little more research I found the answer.

The zig-zag on the leading edge is a type of leading edge extension called a dogtooth extension.

Quote from wikipedia:


  A dogtooth is a small, sharp zig-zag break in the leading edge of a
  wing. It is usually used on a swept wing, but also on straight wings
  ("Drooped Leading Edge" arrangement), to generate a vortex flow field
  to prevent separated flow from progressing outboard at high angle of
  attack. The effect is the same as a wing fence.
  
  Where the dogtooth is added as an afterthought, as for example with
  the Hawker Hunter and some variants of the Quest Kodiak, the dogtooth
  is created by adding an extension to the outer section only of the
  leading edge.