I hate this question: What is your greatest weakness?
Primarily, stupid. Chances are, if I knew of this weakness, I would try to fix it. If it was so crippling or such an important component of my character that I cannot, I doubt it's anything I would want to share with someone who gets a say in whether or not I have a job. Really, it's just a test of your ability to produce bullshit on command.
I've never been able to come up with an answer for it that didn't make me despise myself, so I'd like to go with the following:
What is your greatest weakness?
My immense penis size. At times, the responsibility weighs heavily.*
*Seriously though, my greatest weakness is my inability to accurately measure things.