How thick is the skin of an aircraft like the Airbus A350 or Boeing B777? We can evaluate how thick walls are by looking at door or window frames, however that isn't representative of an aircraft fuselage, which appears to be very thin:


Airbus A350 XWB forward fuselage, source


How thick (thin!) is the fuselage?
Do some areas have a thicker skin for some reason?
What about glass, doors, wings, floors, and other elements than the walls?


(I'm talking about the aircraft skin itself, not stringers or other structural stiffeners.)
From whats written here 


  f100 skin is 1.0 - 1.4mm  
  
  b747 skin is 1.8 - 2.2mm  
  
  a320 skin is about 1.1mm


According this article on the 757


  ...Although Boeing specified that the skin in that area of the
  fuselage must be 0.039in (0.99mm) thick...


Some interesting info here as well.