Best- too many to mention really.
Worst: wheel guide - never used it, never used it to decorate wrapping paper as I envisioned when I purchased it. I have since unmounted my wheels and use them as background stamps and am MUCH happier with that format.
I also don't use my WWC much. Love the watercolor pencils. I know several people swear by the WWC, I am just not one of them. Isn't variety terrific?