I have been using my username for some years now. I have thought of several mods to it, but I'm quite fond of how well it turned out.
My first username that wasn't my ordinary name was simply "Dragon". However, it didn't work out for long... Simply because it was too common, too many people were using it already. So I changed it to Spagon. Which lasted a year, then was abandoned as well.
merlfox, however is ultimate
I believe it qualifies as a pun. merlfox consists of the name of "Merlin", the famous magician, and the animal "Fox". Merlin since I am fascinated by magic and tend to go with a magician when I play RPG's and a fox to show that I rely upon brain rather than brawn. I guess the username also describes my personality since I am a rather calm person and like to ponder upon things...
There it is. My life story.