The idea that you can profile your callers as one of several different archetypes is not, by any means, an original one. This list started when a co-worker told me he had just completed one of the longest 'Columbo calls' of his life. The concept was so fitting that I started looking for more common customer types. The six I have decided on so far:
The Jehovah's Witness - This type of customer is not calling to have you figure out what they need to resolve their issue. They already know the answers and just need you to come around to their way of thinking. This type of caller will not take 'no' for an answer, but instead will keep pushing for the resolution they feel is correct. Unfortunately, they usually only become evident when policy is in direct conflict with their desired result. Like their namesakes they have no qualms about escalating to a higher power. By the end you just want to tell them to get off your porch.
The Scrooge - A Scrooge customer is one that does everything with a view to saving money. They may trim down computer specs to ludicrous amounts just to save a buck and/or argue about every single line item in an invoice. They have been known to become confused and frustrated when they cannot install software because they ordered a computer without a DVD-ROM. And it's your fault, somehow.
The list is subject to change as I come up with better examples/names or new archetypes become apparent.