I've taken a rather fond interest in finding out exactly what I am, and appropriately so.
http://www.humanmetrics.com/cgi-win/JTypes2.asp
I'm an INTP - The Thinker.
"INTPs are known for their quest for logical purity, which motivates them to examine universal truths and principles. They are constantly asking themselves and others the questions 'Why?' and 'Why not?' Clear and quick thinkers, they are able to focus with great intensity on their interests. They appreciate elegance and efficiency in thought processes and require them, even more so, in their own communications. They may be seen as unwilling to accept what everyone else regards as truth. While often low key in outward appearance and approach, the INTP is 'hard as nails' when challenging a truth. INTPs do not like to deal with the obvious. They are at their best in building conceptual models and developing unusual and complex ideas."