Always Working Backwards
An elite brand of coder, the reverse engineer is responsible for many of the freedoms people enjoy these days.
An elite brand of coder, the reverse engineer usually takes a finished product (generally compiled or in a proprietary format), and, through a variety of techniques, is able to understand the inner workings and to apply that understanding in a variety of ways.
Why? Sometimes just for intellectual curiosity. Sometimes from boredom. And sometimes you need to convert a proprietary driver/format for one Operating System and port it to another. Jon recently did this to create a Linux driver for a small receipt printing machine we'll use @ LinuxWorld this year. (Ed. Note: When this was written, it was 2001.)
Of course you don't have to limit the scope of the reverse engineer to formats and compiled code - you can also reverse engineer, say, a Snickers Bar, or even a sheep ;)
Black, 100% cotton t-shirt with 'reverse engineer' printed in reverse on the front.