Personally, I think the Charmander one, the Saphira one, Demonbane's one (the last green one) are the best, closely followed by the Obi-Wan Lego sig if I finished it.
I am actually in the (slow) process of making a tutorial for the Afterlife sig. I'll post it when it is done (eventually).For quite a lot of them I used tutorials, and for the Saphira one I did the unexpected: I used a Sprite Sig Tutorial to make a normal sig.

I can't find the exact Tutorial for the Saphira sig right now, but it was from a collection of sigs (I think made by other people than the one who put it together) which can be found
here.