Was looking over the Halo 4 launch gameplay trailer and found something interesting about the Forerunners, well.... at least the one shown in the trailer, lmao! 
  
  
 
http://www.youtube.com/watch?v=DIspQ1NmGf4&feature=player_embedded
 
 
  
From that trailer I grabbed a few screens of this "Ancient Evil". Now let's count the fingers.  
  
  
 
 
 
  
 
 
 
  
 
 
 
  
  
One...two...three...four...five...six!!! Yes folks, this Forerunner has six fingers!! Well, to be "technical", 5 fingers and a thumb on each hand (which do appear to be opposable, lol)!! The "pinky" isn't viewable in the second screen.  
  
I guess 343I figured five wasn't enough to fully wrap around Chief's head!!  
  
Enjoy!!