I have many feet that I use on my several Pfaff machines. In particular, I have used this 6 mm open toe applique foot for everything over the years. Lots of zig-zaggy things such as satin stitch etc. But lately, I love it for top stitching. Most, if not all of my small projects have some sort of top stitching on it.
This foot has red markings which I use for eye-balling where I want my stitching to be. And the center opening is exactly a quarter of an inch. That means that if I use the edge of the inside of the foot as a guide, and leave the needle in the center position, I will get a nice one eighth inch top-stitching detail.
When I do zippers, I find that one side of this applique foot rides nicely on the zipper tape when doing the stitching. Even as can be.