I think my favorite entry of mine is the one for SOTW #5: Videogames. Yes, it's the one I've been using as my current sig for the past week or so. I love the curves I added to it to. I also think the overlaid speedometer is a great touch.
I think the worst sig out of all the entries in all the contests is probably my Batman Begins rip-off for SOTW #6: Movies. I was going to submit a Fight Club sig at first, but I got so terribly bored with it that I fell back on the last movie I saw at the movies. I did put some semblance of effort into it by replicating the bat logo with the pen tool. It wasn't a fun entry to submit. It was just there. Less boring than the Fight Club one, though.