5. "Help! I forgot my password."
The fella who calls after forgetting his network password is bad enough (especially when you consider that it was probably "password123" to begin with). Worse yet is the guy who calls after forgetting his password to Facebook, Friendster, or -- the crown of them all -- AshleyMadison.com.
Of course, IT does its fair share to encourage this particular brand of brain freeze with increasingly complex password policies, which could be a recipe for disaster.