(2) Used to convey a special uniqueness and/or creativity in cursing.
What the duck do you think you're doing with my gold?
Your 'friend' leaves for a lunch break while you're in the deepest part of the dungeon:
Dude, you totally left me to get pwned all alone! I mean, what the duck?!
A friend makes a decision that suxx0rz:
What the duck is the matter with you?!