There’s one type of caller missing, but most of you guys at tech support never have to talk to those ones anyway. But I did during my tech support months (fyi: service providers and sys admins)

The Sexist
Those are the ones who want to speak to a real expert, not to a woman, but to a man who understands things about Unix, Linux, NetWare etc (any topic except NT, they never asked for a "real" NT expert/engineer. hm). What the hell do they think? That the company hired me just because I’m sexy, or what? No lads, they hired me because I understand “those things”!
They refuse to talk about their computer-related problem, just want to be transferred to the engineer. When you thread them (politely of course) with pressing the release button so that they have to go into the queue again and maybe have more luck next time (aka: talking to a male tech support), they start ranting. That’s where the call ends.