Wow I feel old. I remember almost all of the pieces in this thread, and I remember most of the people who have posted in this thread joining :-P Of course, I've been a lurker the whole time, so whatever. I guess my first piece of pixel art was this for the tesselation challenge:
I remember being massively impressed by Morganne's pegasus tesselation for this challenge. Unfortunately, due to lack of practice, I haven't improved very much at pixel art since then. I can analyze and critique decently after being around it for three years, but my skills at creating it leave something to be desired. Ah, well.