OK, since everyone seems to be doing it, I might as well : )
I have thought about all the various proposals, studied my own dock, and come up with these really quick & dirty mock-ups:
Version 1: Among the best icons in my dock are the Adobe CS icon suite. They are clean, easy to distinguish, yet very detailed. So, I thought I'd start from there.
The 'concept' for this logo came from Justin's "key with cogwheel icon on", that I thought looked too much like iKey's for it to work. So I didn't like that one, but I like the concept of a keyboard key, with a 'gear/cogwheel' on it. I also like the 'Mate', when (s)he is away from the type writer.
The problems in the icon above are: -- the gear in the background of 1a is not obvious enough -- the 'mate' is too detailed to work in smaller sizes. Needs to be simplified, especially in the face, where the eyes & smile need to stand out clearly.
Version 2: A really dirty version of one of the previous icons - created by someone (sorry can't find your name now) - and I really liked the "text document" icon in the background, so I just added the 'mate', so that it became an obvious TextMate.
Neither of these icons works in a small size because of the look of the 'Mate', but think about the overall concepts instead, and think of a better 'Mate' that works in small sizes as well.
Hope the above ideas will in some small way further the cause.
Kind regards,
Mats