I have two favorites; one is bottle and the other is homemade.
The bottled flavor is Henry's FF honey dijon. It's the best of the honey dijon's that I've tried.
The homemade is my mother's FF thousand island. It didn't start out FF but I modified it for Core. If you ever really want a decadent salad dressing to serve to company...make it with all full fat ingredients. I'm not sure if chili sauce is considered Core but I consider it to be Core enough.
Here's the link. You should definitely check out the recipes on our board. CORE Side Dishes & Salads