SBQ - Specialty stitches

What is your favorite specialty stitch? Which one is your least favorite? Why?

I don't do a lot of specialty stitches to be truthful. My least favorite would probably be french knot, because I have yet to master them, no matter how hard I try. I've tried a couple of tutorials, but I think I really need someone hovering over me to show me the ropes, like with beading. My favorite is probably the Holbein stitch or double running stitch for blackwork. There's just something about flipping over your work and seeing the same thing on the other side. At least you know you're doing it right. I seem to remember liking nun's stitch when I used it for the fringe on a couple of bookmark projects.